Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/780

Click to flip

780 Cards in this Set

  • Front
  • Back
accessory mineral
a mineral present in small amounts in a rock, unimportant for rock naming or classification
accesssory plate
a plate that may be inserted in the tube of a polarizing light microscope to produce interference of a known amountl typically made of quartz, gypsum, or mica.
Acicular
having a needle like shape
actinide
elements (such as Th, Pa, and U) with atomic numbers 90 through 103 and valence electrons in 5f orbitals
acute bisectrix
aline bisecting the angle formed by the two optic axes in a biaxial mineral
acute bisectrix figure (Bxa)
the interference figure seen when looking down an acute bisectrix
adamantine
a type of luster that is bright, sparkly, and shiny similary to that of diamonds
aggregate (or crystals)
a mass of crystals, of the same or different minerals, that may be physically separated, perhaps with some difficulty
albite twin
a common twin law in ticlinic feldspars, often resulting in polysynthetic twins
alchemy
chemistry of the Middle Ages that combind science, magic, and philosophy
alkali element
any element (such as Li, Na, or K)of the first group in the Periodic Table of the Elements; alkali elements typically ionize to form monovalent cations
Alkaline earth element
any element (such as Be, Mg, or Ca) of the second group in the Periodic Table of the Elementsl alkaline earth elements typically ionize to form divalent cations
allochromatic
a term descriving a mineral that gets its color from minor or trace elements (see also iodiochromatic)
alloy
a noncrystalline mixture of two or more metals
alluvium
unconsolidated sediment deposited by a stream
amorphous
having a random atomic structure (see also noncrystalline)
amphibolite (facies)
one of the principal metamorphic facies introduced by Eskola, corresponding to high-grade conditions of about 450 - 650 and 3- 8 Kbar
amphibolite (rock)
a metamorphic rock containing primarily hornblende and plagioclase
analyser
a polarizing filter that can be inserted in the upper column of a polarizing light microschope to view minerals under crossed-polarized light (see also upper polarizer)
anatexis
melting of preexisting rock
andesite
an extrusive igneous rock of intermiediate composition containing plagioclase as the only major feldspar; minor K-feldspar or quartz, pryoxene, biotite, and hornblende may be present
angle of incidence
the angle that an impinging ray makes with a normal to an interface
angle of refraction
the angle that a refracted ray makes wit ha normal to an interface
anhedral
a crystal that lacks well-developed crystals faces or that has rounded or irregular form due to crowding by adjacent crystals
anion
an ion having a negative charge
anionic complex
a tightly bonded, negatively charged moleculr group; in mineral formulas, often surrounded by parentheses
anisodesmic
describing an ionic compound in which the ionic bonds are not all of the same strength
anisotropic
having different physical properties in different directions
anomalous interference colors
interference colors that are not represented on the Michel Levy Chart; typically associated with minerals of exteremely low birefringence, such as chlorite
aphanitic
having no mineral grains that are visible to the naked eye
aqueous solution
a water-rich solution, usually containing dissolved elements or complexes
arborescent
a term descrving an aggregate of crystals having a treelike appearance (see also dendritic)
arenite
general term for detrital sedimentary rocks composed of sand-sized grains and lithic fragments; includes sandstone, graywacke, arkose, and others (see also psammite)
arkose
a feldsapr-rich sandstone
asbestiform
a crystal habit characterized by fine threadlike, fibrous, or acicular crystals; more specifically, sometimes defined as a crystal habit with a length:diameter ratio of more thant 3:1
asbestos
a genral term referring to minerals that have an asbestiform habitl chrysotile, amosite, and crocidolite are typical asbestos minerals
association (mineral)
a group of minerals found together in a rock
asterism
the play of colors seen in some minerals that produces a rayed or star-shpaed figure when viewed in direct light; a star sapphire is one example
atmophile
an element that tends to concentrate in the Earth's atmosphere
atomic absorption spectrophotometer
an analytical instrument in which compoistion is determind by measuring the absorption of characterisitc wavelengths of light by an atomized and flamed sample
atomic mass unit (amu)
unit for expressing atomic mass, equal to approximately 1.66x10^-24 grams
atomic number(Z)
the number of protons in the nucleus of an atom of an element
atomic weight
the weight of an atom or compound in atomic mass unitsl generally close to the total number of protons and neutrons
Aufbaur principle
the principle that states that electrons fill orbitals in a systematic way from the lowest energy orbitals to the highest
augen
lagrge lenticular mineral grains or mineral aggregates in a foliated metamorphic rock
augen gneiss
a gneiss containing augen
authigenic
formed or generated in place; used to describe minerals that form in a sediment or sedimentary rock after deposition of an original sediment
Avogadro's number
6.022x10^23, equivalent to the number of atoms or molecules in a mole
Axial ratio
the ration of unit cell lengths along each crystallographic axis, a:b:c
axis (crystallographic)
one of the three edges of a chosen unit cell in a crystall lattice; the coordinate system used to describe points, lines, and planes in a crystal
axis (rotational)
a symmetry element that relate identical crystals faces or other things by rotation of 60, 90, 120, 180, or 360 about an axis
Banded iron formation(BIF)
a layered rock containing chert, silicate, carbonate, or oxide layers, giving a banded appearence
Basal cleavage
a term used to describe the cleavage in minerals such as micas that allows the ineral to break into plates or sheets
Basalt
an extrusive igneous rock of mafic composition containing plagioclase as the only major feldspar; clinopyroxene plus or minus orthopyroxene plus or minus olivine are typically present (see also gabbro)
basement (rock)
metamorphic and igneous rocks that underlie sediments and sedimentary rocks observed at the Earth's surface; often, though not exclusively, of Precambrian age
basis
a sufficient set of symmetry operators for descriving the symmetry of crystals (translation-free symmetry) or of atomic structures (space sysmmetry)
bauxite
name given to a rock or a mineral-like material composed primarily of a mixture of aluminum oxides and hydroxides such as boehmite and gibbsite;l bauxite is the most significant aluminum ore
Baveno twin
an uncomomon twin law in feldspar
Becke line
a bright line, visible under a microscope, that separates substances of different refractive indices
bentonite
a clay-rich earthy materal formed by devitrification and alteration of tuff or volcaing ash; sometimes used more generally to refer to any clay deposit rich in montmorillonite
Berman blaance
a type of balance scale used to determine specific gravity
Betrand lens
a lends that can be inserted in the tube of a polarizing light microscope to facilitate observation of interference figures
biaxial
describing a crystal having two optic axes and three principal indices of refraction. Such crystals belong to the orthorhombic, monoclinic, and triclinic crystal systems
binary solution
a solid solution series that can be characterized by two end members
birefringence (property)
the property of a crystal that causes double refraction
birefringence (value)
the difference between the greatest and least indices of refraction
bladed
having the appearance of blades
blocky
a term used to describe crystals that have a blocklike appearance, generally with an approximately square cross section
blueschist (facies)
one of the principal metamorphic facies introduced by Eskola, corresponding to high pressure-low temperature conditions
blueschist (rock)
a vague term used to describe fine grained, bluish colored rock diagnostic of the blueschist facies. Key minerals include blue amphiboles (glaucophane and riebeckite), lawsonite, jadeite, and aragonite.
body centered
said of a unit cell that has an extra lattice point at its center
body diagonal
aline passing through the center of a cube or other three-dimensional geometric shape and connecting opposite corners
Bohr model of the atom
a fundamental model of an atom that states that electrons orbit atomic nuclei in orbits associated with specific energy levels
bomb
a laboratory reactor vessel used to synthesize gems and minerals at high pressure and temperature
bort
dimond of low quality that is unsuitable as a gem but useful in industrial applications
botryoidal
a term used to describe a mineral habit that appears like a bunch of grapes
boule
a oblong-shaped synthetic mineral crystal that is produced from the Verneuil technique
Bowen's reaction series
a hypothetical series that describes the order of crystallization of minerals from magma
Bragg law
a mathematical law that describes the relationship between the angle of diffraction, x-ray wavelength, and atomic plane spacing
Bravais lattices
the fourteen possible three-dimensional lattices that can describe mineral structures
Brazil twin
a common type of twinning in quartz
Breccia
a clastic sedimentary rock composed of large angular broken rock fragments in a finer grained matrix
Bridging oxygen
an oxygen atom in a crystal structure that is shared by two or more equivalent coordinating polyhedra
brittle
a term used to describe minerals that shatter or break easily when struck
brucite layer
a sheet of Mg(OH)6 octahedra in a layered crystal structure
Buerger precession camera
an instrument designed to record single crystal diffraction patterns on film
burial metmorphism
metamorphism affecting a large region; caused by pressure related to depth in the Earth and temperature related to geothermal gradient (see also regional metamorphism)
Cabochon
a gemstone that has been ground and polished into a domed shape
calcine
the heat material, such as limestone, to high temerature, breaking down minerals and driving off carbon dioxide or other volatiles
capillary
having a hairlike or threadlike appearance (see also filiform)
carbonate (mineral)
a group of minerals with formulas characterized by (CO3) 2- radicals
Carbonate (radical)
the (CO3) 2- anionic group
Carbonate (rock)
a chemical sedimentary rock dominated by carbonate minerals; limestone or dolostone
Carbonation reaction
reaction of a mineral or minerals with CO2 to produce a product carbonate mineral
Carlsbad twin
a commmon twin law in orthoclase, less common in other feldspars, often resulting in penetration twins
Cartesian coordinate system
an X-Y-Z coordinate system in which all axes are at 90degree and the unit distances along all axes are equal
Cataclastic metamorphism
metamorphism caused by a transient high-pressure condition such as a meteor impact (see also shock metamorphism and dynamic metamorphism)
Cathode ray tube
Vacuum tube in which beams of high-energy electrons pass through magnetic fields and hit a fluorescent screen
cation
an ion having a positive charge
cementation
lithification of clastic sediments resulting from the deposition or precipitation of minerals in the spaces between individual clastic grains; it may occur at the time of deposition or during diagensis
centered
said of a unit cell that has (an) extra lattice point(s) at its center, in the center of its faces, or in the center of two opposing faces..
chain silicates
silicate minerals characterized by SiO4 tetrahedra joining to form chains either one tetrahedron or two tetrahedra wide (see also inosilicates)
chalcophile
an element that tends to concentrate in sulfide minerals and ores
characteristic radiation
high-intensity radiatioin of one or a few wavelengths emitted by the target of an X-ray tubel the wave length(s) or characteristic radiation depend on the elements in the target
chatoyancy
the play of colors seen in some minerals in which a silky sheen is seen to form a narrow band that changes position as the mineral is turned; for example cat's-eye chrysoberyl
chemical precipitate
a solid that precipitates from an aqueous solution, typically due to supersaturation
chemical sedimentary rock
a sedimenatray rock composed primarily of material formed by precipiation from solution; for example, most limestones and all evaporites
chemical sediments
sediments produced by dissolution and precipitaion resulting from chemical weathering; they may precipitate where weathering occurs or at a different place
chemical weathering
type of weathering involving chemical reactions that transform or decompose miinerals and rock
chert
a hard sedimentary rock composed primarily of cryptocrystalline silica, generally in the from of cibrous chalcedony with lesser amounts of quartz and opal
chromophores
elements that give minerals their color
clast
a mienral grain, lithic fragment, or organic remnant that is produced by mechanical weathering and bcomes part of a clastic sediment or rock
clastic
being composed of grafments (clasts) derived from preexisting rocks
clastic rock
sedimentray rock formed by the lithification of clsatic sediments; for example, sandstone, shale, and siltstone
Clausius-Clapeyron equation
an equation relating the slope of a reaction on a prssure-temperature diagram to the entropy volume change of the reaction
clay (grain size)
a clastic fragment of any cmposition smaller than silt, having a dimaeter less that 1/256 mm
clay (mineral)
member of a group of loosely defind hydrous sheet silicates formed primarily by alteration or weather of primary silicates. The most common clays belong to the illite, jaolinite, or montmorillonite groups
cleavage
the breaking of a mineral along a set of parallel identical atomic planes
clinonet
a two-dimensional lattice characterized by two translations of different magnitudes at nonspecial angles to each other
clinopyroxene
monoclinic pyroxene subgroup dominated by end members diopside and hedenbergite. The most common of all pyroxenes
closet packing
the most effecient way to pack like atoms together in three dimensions; each atom is surrounded by 12 others
colloform
appearing as spherical or hemispherical shpaes made of radiating crystals (see also globular)
color
a sensation produced by different wavelengths of light hitting the eye
columnar
having the appearance of an aggregate of slender, elongated individual crystals, nearly parallel in arrangement
complex twin
a twin composed of more than two individual crystals
compositional zoning
variation in the composition of a crysta, typically from core to margin (see also zoning)
compound (chemical)
a substance of fixed atomic proportions made by the combination of two or more elements
concentration fact
the extent to which an element must be concentrated above normal crustal levels to make minig it profitable
conchoidal
a term describing fracturing that produces curvged surfaces similar to when glass breaks; for example, quartz has a conchoidal fracture
condenser
a lens, or several lenses, that may be inserted in the substage of a polarizing light microscope to cause light rays to converge on a sample (see also condensing lens)
condensive lens
see condenser...
conglomerate
a coarse-grianed clastic sedimentary rock with fragments larger that 2 mm in diameter in a fine-grained matrix; the equivalent of lithified gravel. The clats are rounded in conglomerates in contrast with breccias
conoscopic illumination
describing the strongly convergent light produced by the insertion of a condensing lens in a polarizing light microscope substage
constructive interference
the addition of two waves that are in phase with negligible or no loss of energy
contact aureole
a contact metamorphic zone surrounding an igneous intrusion (see also aureole)
contact metamorphism
metamorphism localized around an igneous rock body; primarily in response to heat and flowing fluids.
Contact twin
a twin in which two individuals are symmetrically arranged about a twin plane
Continuous radiation
the low-intensity radiation covering a range of wavelengths , produced by and X-ray tube; continuous radiation provides the background for characteristic radiation
continuous side (Bowen's reaction series)
the side of Bowen's reaction series characterized by plagioclase
coordinating polyhedron
polyhedron formed around an atom or ion by ocnnecting the centers of the coordinated atoms or ions
coordination number
number of neighboring atoms to which and atom is bonded
country rock
rock intruded by and surrounding an igneous intrusion
coupled substitution
simultaneous substitution of two or more different ions in a structure in such a way that charge balance is maintained; for example, the substitution of Ca, Al, for ?Na, Si, in albite
covalent bond
an ideal chemical bond that involves the sharing or orbital electrons between elements that have little or no difference in electronegativity
cover slip
a thin piece of glass that is placed over grains and liquid to make a grain mount
critical angle
the angle of incidence that yields an angle of refraction of 90 degrees
crossed polars
the condition caused when the upper polarizer is inserted in a polarizing light microscope
cryptocrystalline
a term describing a material containing generally submicroscopic grains whose crystalline nature is not easily determined
crystal
a homogenuous solid body of an element, compound, or solid solution having a regularly repeating atomic structure that may be outwardly expressed as planar faces
crystal classes
the 32 possible combinations of symmetry elements that a crystal may have; in modern usage, practically synony mous with the 32 possible point groups
crystal morpholofy
the shape and form(s) of a crysral
crystal structure
spatial arrangement of atoms or ions, and their bonds in a crystal
crystal structure determination
determination of the spatial arrangement of atoms and their bonds in a crystal
crystal system
one of the six distinct coordinate systems: cubic, orthorhombic, tetragonal, hexagonal, monoclinic, and triclinic. The trigonal subdivision of the hexagonal system is sometimes counted as separate crystal system.
crystalline
having a crystal structure; having a regular arrangement of atoms characterized by a space lattice
crystallographic axis
a direction corresponding to one of the three edges of a chosen unit cell in a crystal lattice
cube
a closed form of six identical square faces of 90degree to each other
cubic
having a cube shape or belonging to the cubic system
cubic (coordination)
the bonding of an ion to eight others arranged so that connecting their centers forms a cube
cubic (system)
a crystal system characterized by lattice symmetry 4/m32/m and containg point groups with symmetry no greater than 4/m32/m; one cell parameter (a) is needed to describe the shape and size of a cubic unit cell
cubic closest packing
closest packing of atoms in a pattern similar to a face-centered cubic lattice; closest packing equivalent to stacking closest packed layers in an ABCABC sequence
cumulate
a layer of minerals accumulated by gravity settling of crystals as they form in a magma chamber
cyanide method
a method for extracting valuable metals from ore that involves hydrogen cyanide
cyanide method
a method for extracting valuable metal ore that involves hydrogen cyanide
cycle
one complete upward and downward motion by a wave
cyclic twinning
repeated twinning of three or more individuals according to the same twin law but with the twin axes or twin planes not parallel, usually producing a twinned crystal in which twin domains are related by aparent rotational symettry
cyclosilicates
silicate minerals characterized by SiO4 tetrahedra joining to from rings (see also ring silcates)
Czochralski process
a method of making synthetic gems that involves a seed crystal drawing materals out of a melt
d-value
the distance betwen adjacent planes with the same Miller indices
dacite
an extrusive igneous rock of silicic composition that contains more plagioclase than K-feldspar; biotite and hornblende are typically present (see also granodiorite)
daughter element
the product element of radioactive decay
daughter isotope
the product isotope of radioactive decay
Dauphine twin
a common type of twinning in quartz
Debeye-Scherrer camera
the most commonly used and most versatile camera for obtaining powder diffraction patterns
decarbonation reaction
a reaction that liberates CO2 from a mineral
defect
a flaw in an otherwise ideal crystal structure
degrees of freedom
the number of intensive variables that may be changed independently without causing a change in mineral assemblage or composition
dehydration reaction
a reaction that liberates H2O from a carbonate mineral
dendritic
a term describing an aggregate of crystals having a treelike appearance (see also arborescent)
density
he quantity of matter in a unit volume; mineral densities are typically given in units of gm/cm3
destructive interference
the addition of two out-of-phase waves resulting in a total, or significant, loss of energy
detrital
referring to a product of mechanical weathering
detrital sedimentary rock
rock formed by lithification of detrital sediments
detritus
broken-up material resulting from mechanical weathering
detrital sedimentary rock
rock formed by lithification of detrital sediments
detritus
broken-up material resulting from mechanical weathering
diagenesis
chemical, physical, and biological changes that affect sediment or sedimnetary rocks after initial deposition, but excluding weathering or metamorphism
diamagnetism
a property of minerals that causes a small negative reaction (repulsion) to a magnet
diamond (shape)
a parallelogram having four sides of equal length and no angles at 90 degrees
diamond lattice
see diamond net
diamond net
a two-dimensional lattice characterized by two translations of the same magntude at nospecial angles to each other
disphaneity
the ability of a mineral to transmit light; often described as transparent, translucent, or opaque
diaphragm
an adjustable opening used to control the size of a light beam in a polarzing light microscope
dichroism
pleochroism of a mineral that is observed as two different colors
diffraction
apparent bending of radiation by evenly spaced atoms, slits, or gratings
diffraction grating
a grating that causes diffraction
diffraction slit
a slit that causes diffraction
diffractometer
an instrument that recods x-ray diffraction patters
dioctehedral
describing a layered mineral structure in which only two or three available octahedral sites are occupied
diorite
an intrusive igneous rock of intermediate compositio containing plagiocalse as the only major feldspar; minor K-feldspar or quartz, pyroxene, biotite, and hornblende may be present
diploid
a closed cubic form of 24 quadrilateral faces; a from of crystal class 2/m3
dipyramid
a closed crystal form of 6, 8, 12, 16 or 24 faces, comprising two pyramids related by a mirror plane of symmetry
discontinuous side (Bowen's reaction series)
the side of Bowen's reaction series characterized by olivine-pyroxene-anphibole-biotite
disequilibrium
dispersion
dispersion
a difference in wave velocity for different wave lengths
disphenoid
a closed crystal form comprising two sphenoids related by 222 symmetry
disseminated deposit
an ore deposit in which the ore mineral is scattered throughout a host rock
dissolution
the process of dissolving
divalent
having a charge of -/+ 2
divariant field
a region on a phase diagram characterized by two degrees of freedom
divergent (crystals)
slender crystals emanating from a common point (see also radiating)
dodecahedral (coordination)
12-fold coordination
dodecahedron
a closed cubic form of 12 faces that may have any of a number of shapes and point group symmetries
dolostone
a chemical sedimentary rock composed primarily of dolomite
domain
a region within a crystal having a structure or orientation that differs from other regions within the crystal
dome
an open crystal form composed of two nonparallel faces related by a mirror
dop
a sticklike device that holds a gem crystal for grinding on a wheel
double chain silicates
silicate minerals characterzied by SiO4 tetrahedra joining to form chains two tetrahedra wide (see also amphibole)
double refraction
the ability of a mineral to split ordinary light into two waves of different velocities and polarization
doubly primitive
term describing a unit cell containing a total of two lattice points
drusy
having surfaces coated with fine crystals
ductile
a term used to describe the tenacity of mienrals that are capable of being drawn into a wirelike shape
dull
a type of luster that does not reflect significant amounts of light or show any play of colors
dunite
an ultramafic intrusive rock in which the only major mineral is olivine; chromite is typicall ypresent as an accessory mineral
dynamic metamorphism
metamorphism caused by a transient high-pressure condition such as a meteor impact (see also shock metamorphism and cataclastic metamorphism)
E-ray
see extraordinary ray
eclogite (facies)
a high-pressure/high-temperature metamorphic facies characteristic of the mantle
eclogite(rock)
a high pressure/high-temperature rock containing Mg-rich garnet (pyrope) and Na-rich clinopyroxene (omphacite); mostly of mantle origin
edge diagonal
a line passing through the center of a cube or other three-dimensional geometirc shape, and connecting the centers of opposite edges
edge dislocation
a kind of line defect caused by a terminated roc of atoms
edge sharing
the sharing of two atoms or ions by two adjacent coordinating polyhedra; the coordinating polyhedra appear to be sharing an edge
effective ionic radius
radius of a spherical volume effectively occupied by an ion in a particular structure
effervescence
a bubbling reacton; the term used to describe the reaction of calcite with dilute hydrochloric ace
elastic
a term used to describe mienrals that return to their original shpae after bending
electromagnetic radiation
emission or transfer of energy in the form of waves; includes x-rays, visible light, infrared light, radiowaves, and television waves
electron
an extremely small atomic particle having little mass and the smallest negative electric charge occurring in nature. Atoms have electrons orbiting around a nucleus.
electron cloud
the space occupied by electrons surrounding an atomic nucleus
electron cloud
the space occupied by electrons surrounding an atomic nucleus
electron microprobe
an analytical instrument in which a finely focused electron beam hits a sample, causing emission of elemental characterisitc radiation
electronegativity
measure of the tendency of elements to acquire electrons
electrostatic valency principle (Pauling's rule 2)
the strength of an ionic bond is equal to its ionic charge divided by its coordination number
element
a basic chemical unit composed of atoms having the same atomic number; elements cannot be separated into simpler parts by chemical means
elliptic
a term describing crystals that are very small ellipsoids
enantiomorphic
a term describing two crystals whose atomic structues are mirror images of each other
end centered
a term describing a unit cell with an extra lattice point in each of two opposing faces
end member
an ideal chemical formula representing one limit of a solid solution
energy level
the enrgy associated with a particular electron orbit in an atom
enthalpy
a thermodynamic variable related to the Gibbs free energy
entropy
a thermodynamic variable representing the degree of randomness or disorger in a system
epigenetic
refers to a mineral deposit that is emplaced after its host rock already exists
equant
having approximately the same dimensions in all directions
equilibrium
a static state of a chemical system in which the relative amounts and compositions of phases present do not undergo changes with time
essential mineral
a ineral in a rock that is necessary for the rock to be classified or named as it is
euhedral
a crystal that is completely bounded by well-developed crystal faces and whose growth was not restrained by adjacent crystals
evaporite (mineral)
minerals that may form by precipitation from aqueous solutiom under norma Earth surface conditions; for example massive gypsum or salt beds
evaporite (mineral)
minerals that may form by precipitation form aqueous solution under normal Earth surface conditions; for example halite, sylvite, and gypsom
evaporite (rock)
a chemical sedimentary rock formed by evaporation of water; for example massize gypsum or salt beds
evaporite deposit
mienral deposit formed by evaporation of water
even (fracture)
a fracutre that produces smooth planar surfaces
exhalitive
a hydrothermal deposit created at the Earth's surface; generally one that forms on the ocean floor from springs
expandable clay
one of a group of clay minerals (smectites) that can exdpand their structure to accommodate excess water or other chemical components
exsolution
the separating of an initially homogeneous mineral solid solution into two (or more) zones of distinct mineral phases; for example, the formation of perthit from an homogenous feldspar during cooling
exsolution lamellae
fine parallel zones of different compositions resulting from exsolution
extinct (mineral grain)
a term describing a birefringent mienral grain oriented so that it appears dark when viewed under crossed polars
extinct (x-ray peak)
a term describing an x-ray peak missing from a diffraction pattern due to destuctive interference
extinction
the systematic absence of a related group of x-ray peaks in a diffraction pattern
extinction angle
the angle, measured under crossed polars, between the position of extinction and a cleavage, long dimenision, or other direction in a crystal
extraordinary ray
in a uniaxial crystal, the ray of light that vibrates in a plane containing the optic axis
extrusive rock
an igneous rock that crystallizes at or very near the Earth's surface (see also volcanic rock)
face centered
a term describing a unit cell with an extra lattice point in the center of each of its faces
face sharing
the sharing of three atoms or ions by two adjacent coordinating polyhedra; the coordinating polyhedra appear to be sharing a face
facet
a polished face on a gemstone
facies (metamorphic)
a range of pressure-temperature conditions characterized by one or more specific mineral assemblages
family of planes
an infinite number of planes, parallel and spaced equally, all characterized by one or more specific mineral assemblages
fast ray
the fastest of two rays produced by double refraction
feldspathic
an adjective describing a mineral aggregate containing feldspar
felsic
a general adjective referring to igneous rocks having light colored minerals in their mode
feroomagnetism
a type of magnetic order, characteristic of iron, that causes a mineral to respond strongly to a magnetic field
fibrous (cleavage)
a term describing a cleavage that allows crystal to be broken into fibers
fibrous (crystals)
having the appearance of being composed of fibers
filiform
having a hairlike or threadlike appearance (see also capillary)
fissility
the rock property of breaking easily along closely spaced planes; often used to describe shale or schist
flash figure
the interference figure observed when the optic axis (uniaxial mineral) or the optic plane (biaxial minera) are oriented parallel to the stage of polarizing light microscope
flexible
a term used to describe the tenacit yof mineral that are bendable
flood basalt
a laterally extensive and thick lava flow of basaltic composition
fluorescence
a type of luminescence that occurs when minerals are exposed to ultraviolet light, xrays, or cathode rays, but ceases when the exposure ceases
flux
a substance added to promote a chemical reaction or to lower the melting temperature of a material without changing the chemistry of the important phases that are present
flux method
a method of synthesizing gems or other mienrals by growing them in an inert flux
foliated
having planar or sheetlike properties
foliation
a planar fabric or texture
fool's gold
common name foor pyrite
form
a set of identically shpaed crystal faces related by symmetry
fractional crystallization
separation of a crystallizing magma into parts by the successive crystallization of different minerals (see also partial crystallization)
fracture
breaking of a mienral other than along planes of cleavage
framework silicates
silicate minerals characterized by SiO4 tetrahedra joining to form three-dimensional networks (see also tectosilicates and network silicates)
Frenkel defect
a defect caused when an atom in a crystal structure is displaced from its normal position to a different position
gabbro
an intusive igneous rock of mafic composition containing plagioclase as the only major feldspar; clinopyroxene +/- orthopyroxene +/- olivine are typically present (see also basalt)
gamma rays
electromagnetic radiation of higher energy and shorter wavelength than X rays; emitted by atomic nuclei
gangue
the waste minerals in an ore deposit
gem
an especialy fine or superlative specimen, often mineralogical origin, usually having superb color, light properties, or shape; often a cut-and-polished stone that has value due to beauty, durability, rarity, or size; generally for use in jewelry or for ornamentation
gemmy
having a gemlike appearance; typically having a bright color, an attractive luster, or geometric shape
gemstone
a gem of mineralogical origin
general angle
a nonspecial angle between crystal faces or symmetry elements
general form
for a given point group, a form that has the maximum possible number of faces and whose faces and face normals do not intersect at special angles
general point
on a stereo diagram, a point that is located at a general position, not coincident with an inversion center, a rotational axis, or a mirror plane
geode
a hollow or partly hollow rock cavity lined by mineral material
geothermometer
a mineral or mineral sstem with compositional variations that reflect the temperature at which it formed
Gibbs free energy
a termodynamic variable that describes the relative stability of a mineral or a mineral assemblage; also refers to the energy change associated with a chemical reaction
Gibbs phase rule
a consequence of the laws of thermodynamics: for any chemical system in equilibrium, the number of chemical components plus two is equivalent to the number of stable phases plus the number of degrees of freedom
gibbsite layer
a sheet of Al(OH)6 octahedra in a layered crystal structure
glass
an amorphous solid material; in most cases, a metastable supercooled liquid
glide plane
a compound symmetry operation that repeats a motif or other entity after a reflection
glide plane
a compound symmetry operation that repeats a motif or other entity after a reflection and translation are combined
globular
appearing as spherical or hemispherical shapes made of radiating crystals (see also colloform)
gneiss
a foliated metamorphic rock showing contrasting bands of light- and dark-colored minerals
Goldich's weathering series
a hypothetical serires that describes the order of wetahering of mineral in outcrop; the series is essentially the opposite of Bowen's reaction series
goniometer
a calibrated instrument used to measure the angles btween crystal faces, cleavages, or other planar features in crystals. Simple goniometers consist of a protractor attached to a rotatable ruler
grade (metamorphic)
the degree of metmorphism; generally equivalent to the temperature of metamorphism (see also metamorphic grade)
grade (ore)
the concentration of ore minerals or elements in ore rock
grain mount
mineral grains on a glass slide surrounded by a liquid and covered with a cover slip
granite
an intrusive igneous rock of silicic composition containing10% to 50% quartz and K-feldsapr as the major feldspar; plagioclase, biotie, and hornblende may be present (see also rhyolite)
granitic
a general adjective applied to any light-colored intrusive igenous rock or to any rock composition that generally resembles that of a granite
granodiorite
an intrusive igneous rock of silicic composition that contains more plagioclase than K-feldspar, biotite and hornblende are typicall present (see also dacite)
granular
cojmposed of many small grains
granulite (facies)
the metamorphic facies corresponding to the highest grades of regional metamorphism
granulite (Rock)
a high-grade metamorphic rock containing orthopyroxene
gravel
clastic materal with grains greater that 2 mm in diameter, may include boulders, cobbles, pebbles, or granules
graywacke
general term used for clastic sedimentary rocks similar to sandstones but containing an inordinant amount of clays, rock fragments, or other material in addition to quartz and feldspar
greasy
a type of luster describing crystal faces or other surfaces that reflect light and give of play of colors similar to oil on water
greenschist
a medium-grade metamorphc rock characterized by schistosity and green mienrals including actinolite, chlorite, and epidote
greenschist (facies)
a medium-grade metamorpich facies characterizing conditions of about 300-500 C and 2-8 Kbar
greenstone
a vague term used to describe any fine-grained low-grade green metamorphic rock; generally of basaltic composition
greenstone belt
a metamorphic terrane characterized by the presence of low-grade metamorposed volcanics and volcanogenic sediments and silicic to intermediate plutons
group (of elements)
the elements of one column in the Periodic Table of the elements
group (of minerals)
minerals within a class or subclass that share major chemical or structural features
gypsum plate
a accessory plate, made of gypsoum, for a polarizing light microscope
gyroid
a cubic form of 24 irregular pentagonal faces; a form of crystal class 432
habit
the characteristic appearance of a mineral due to crystal form or combinations of forms, crystal intergrowths, and aggreagates and any other irrefular physical characteristics
hackly
a term describing fracturing that produces jagged edges
halide
mineral compound characterized by a halogen such as F, Cl, or I as an anion
halogen
elements (such as F, Cl, and Br) in the seventeenth group of the periodic table of the elements; halogens typically ionize to become monovalent anions
Hanawalt method
a systematic method for matching an "unknown" x-ray pattern with one in a reference data set such as the Powder Diffraction File
hand specimen
a piece of rock or mineral convenient for studying macroscopic properites, that can be picked up in the hand
hard radiation
x rays of extremely high energy; used in industry and manufacturing but generally not by crystallographers
hardness
the resistance of a mineral to scratching
Haiiy's Law
a law that states that crystal faces make simple rational intercepts with crystallographic axes; a corrolary is that crystal faces have rational and general small Miller indcies (see also Law of Rational indices)
heavy liquid
a liquid of greater density than water that may be used to separate minerals of different densities
heft
an estimation of a minera's density obtained by picking up the mineral and holding in your hand
Heisenberg uncertainty principle
a principle stated by Werner Heisenberg that says it is impossible to know the location and motion of an electron in an atom without some uncertainty
Hermann-Mauguin symbol
a shorthand notation for the symmetry of a point group
hexhonal
of or a related to the hexgonal system
hexagonal (system)
a crystal system characterized by lattice symmetry 6/m2/m2/m, and containing point groups with symmetry no greater than 6/m2/m2/m; two cell parameters (a,c) are needed to describe the shape and size of a hexagonal unit cell
hexagonal closet packing
closest packing of spheres in an orrangement similar to a hexgonal prism with three extra spheres in its interior; equivalent to stacking closest packed layers in an ABABAB sequence
hexagonal packing
packing of identical spheres in a plane so that each is surrounded by six others
hexhedron
a form of six equivalent faces related by symmetry; for example, a cube or rhombohedron
hexanet
a two-dimensional lattice characterized by two tranlations of equal magnitude of 60degrees to each other
hexoctahdron
a cubic form of 48 triangular facesl a form of crystal class 4/m32/m
hornfels
a fine-grained metamorphic rock lacking foliation or lineation
host rock
the rock tht hosts ore minerals or an ore deposit
hydration reaction
a reaction between minerals, or minerals, and water that results in a product hydrous mineral
hydrogen bond
a type of electrostatic bond that is generally insignificant in minerals. Prominent in ice and, to a lesser extent, in micas and hydroxides
hydrolyaste
the material that goes into solution during chemical weatherin
hydrolysis reaction
a type of weathering reaction that simultaneously produces dissolved material and secondary minerals
hydrothermal
having to do with warm water-rich fluids
hydrothermal fluids
hot water-rich fluids that circulate through the Earth
hydrothermal ore deposit
an ore deposit precipitated by hydrothermal fluids
hydroxide
a chemical group, or group of minerals, with formulas characterized by the radical (OH)-; for example, gibbsite, Al(OH)3
hypothesis
a propsoed explanation for an observed set of facts
idiochromatic
term describing a mineral that gets its color from its major elements (see also allochromatic)
igneous
an adjective describing a rock or mineral that solidified form a magma or describing the process that forms such a rock or mineral
immersion method
a method for determining index of refraction by ommersing a grain in liquid or known index of refraction
immiscibility
an inability of tow or more phases to dissolve completely in one another
impurity defect
a defect caused when a foreign atom is present in a crystal structre
inclined extinction
extinction when a principal cleavage or length of a crystal is at an angle to the crosshairs of a polarizing light microscope
incompatible element
an element that does not readily enter a crystal structure
index (indices)
number (numbers) used to describe the location of points, the riention of line, or the orientation of planes in space
index (x-ray pattern)
to assign appropriate (hkl) vlaues to x-ray diffraction peaks
index mineal
a mineral characteristic of a particular set of pressure-temperature conditions for rocks of a given composition
index of refraction
the ration of the velocity of light in a vacuum to the velocity of light in a crystal, glass, liquid, or other medium (see also refractive index(
inert gas
any of the generally unreactive elements (such as Ne, Ar, or Kr) in the eighteenth group of the PEriodic Table of the Elements (see also noble gas)
infrared light
electromagnetic radiation with wavelengths slightly greater than visible light
inorganic
a general term used to refer to compounds that contain no carbon bonded to hydrogen as essential components
inosilicates
chain silicates; either pyroxenes, pyroxenoids, or amphiboles
integral molecules
the fundamental and indivisible building blocks making up crystals, according to Ha,y: now known not to exist as Ha,y envisioned them
intensive variable
a termodynamic variable, genrally pressure or temperature, that is controlled from outside a chemical system
interfacial angel
the angle between two faces of a crystal
interference
the interaction of two waves traveling in the same direction
interference colors
the colors displayed by a birefringent crystal when viewed under crossed polars
intergranular fluid
a fluid between grains in a rock
intergrowth
two or more crystals grown together
intermediate igenous rock
an igneous rock of composition intermediate between mafic and silicic
internal energy
a thermodynamic variable related to Gibbs free energy
internal reflection
the reflection of a light ray back into the interior of a crystal when it reaches a crystal boundary from within
interstice
a space between grains in a rock or between closest packed atoms in a structure
intrusive rock
an igneous rock that crystallizes at depth in the earth (see also plutonic rock)
invariant point
a point on a phase diagram at which two or more reactions intersect
inversion
a term describing the operation that relates two crystal faces or other entities that are equal distant from a central point and have upside-down and backward orientations with respect to each other
inversion center
a point at the center of a crystal (and its atomic structure) through which every aspect of the crystal (and its atomic sructure) is repeated by inversion
ion
an atom with a negative or positive electric charge as a result of having lost or gained one or more electrons
ionic bond
an ideal chemical bond, electrostatic in nature and formed between elements that have large differences in electronegativity
ionic charge
the number of electrons lost of gained when an atom becomes ionized
ionic crystal
a crystal in which the predominant bonding is ionic
ionic radius
radius of a spherical volume effectively occupied by an ion in a particular environment
iridescence
the display of rainbowlike colors in the interior or on the surface of a mineral
iron formation
general name given to chemical sedimentary rocks dominated by iron oxides, hydroxides, carbonates, sulfides, or silicates
irregular (fracture)
a fracture that produces rough and irregular surfaces (see also uneven fracture)
isochrome
color bands that wrap around the trace of the optic axis (uniaxial mineral) or the optic axes (biaxial mineral) in an interference figure
isodesmic
describing a crystal in which all bonds are ionic and of equal strength
isogonal
a term describing space groups that contain the same rotation axes; also used to descrbie space groups that have the same symmetry when translation is ignored
isograd
any line based on mienral or mineral-assemblage occurences that can be mapped in a metamorphic terrane
isogyre
a band of extinction in a interference figure that appears where light vibration directions are parallel and perpendiculoar to the lower and upper polarizers
isolated tetrahedral silicates
silicate mienrals characterized by individual SiO4 tetrahedra linked by bonding to common cations.
isomorphous series
a solid solution series in whcih the crystal structure is the same throughout the series
isostructural
a term describing two minerals that have differnt, but identically arranged, atoms in their crystal structures
isotope
one of two or more species of the same chemical element; different isotopes of an element have the same number of protons but vary in their number of neutrons
isotropic
having the same properites in all directions
join (phase diagram)
a line that connects two end member compositions on a ternary phase diagram
Jolly balance
a type of balance scale used to determine specific gravity
Kimberlite
an alkalic peridotite associated with diatremes, typically containing phenocrysts of olinvie and phlogopite or their alteration products
Komatiite
a general name given to a lava of ultramafic composition
Labradorescence
a flashing and laminated iridescence, generally of a single bright hue, similar to that displayed by labradotie, a plagioclase feldspar
lamellar
having a tablike appearance; being thin in one dimension compared to the other two (see also platy and tabular)
lanthanide
elements (such as Ce, Pr, and Nd0 with atomic numbers 58 through 71 and valence electrons in 4f orbitals (see also rare earth elements)
laterite
a highly weathered and leached soil or subsoil rich in aluminum, iron, or other insoluble elements; often rich in quartz and clay minerals
latite
an extrusive igneous rock of intermediate composition containing approximately equal amounts of plagioclase and K-feldspar; minor quartz, clinopyroxene, biotite, and hornblende may be present
lattice
a three-dimensional representation of the translational symmetry of a crystal structureq
lattice point
translationally equivalent points in space; in a crystal lattice, points are surrounded by identical and indistinguishable atomic arrangements
Laue equations
equations derived by von Laue that describe the angular relationship between an incident beam and a diffracted beam in three-dimensional space
Laue method
x-raying a single crystal by placing it in the pat of a polychromatic x-ray beam and positioning a flat piece of film behind it
lava
molten extrusive magma
lava flow
a horizontal outpouring of lava from a vent or fissue
law of definite proportions
a general law that says compounds are made of elements combined in specific proportions
Law of Bravais
an observational law that states faces on crystals tend to be parallel to planes having a high lattice point density
Law of Rational Indices
a law that states that crystal faces make simple rational intercepts with crystallographic axes; a corollary is that crystal faces have rational and generally small Miller indices (see also Hauy's Law)
laws (scientific)
a formal statement of general scientific observations that have never been found to be violated
layer silicates
silicate minerals characterized by SiO4 tetrahedra joining to form sheets; includes micas and clays (see also sheet silcates and phyllosilicates)
leach
to dissolve and remove soluble components from a rock or soil
left handed
a relative phrase, referring to objects that rotate or point to the left
length fast
a term describing a birefringent mineral in which the fast ray vibrates more or less parallel to the length of an elongate crystal
length slow
a term describing a birefringent mineral in which the slow ray vibrates more or less parallel to the length of an elongate crystal
lime kiln
long horizontal cylindraical furnace used to heat limestone in order to make lime (CaO)
limestone
a chemical sedimentary rock composed primarily of calcite; in a more general sense the term is sometimes used to refer to any chemical sedimentary rock composed mostly of carbonates
line defect
a kind of defect that occurs along a line in a crystal structure
lineage structure
a plane within a crystal separating slightly misoriented portions of a crystal structure
linear(coordination)
coordination of a small ion or atom to only two others
lineation
any linear feature that may be obseved in a rock
liquidus
the line on a temperature-composition diagram that shows the temperatures above which a system is completely liquid
lithic fragment
clastic fragment of preexisting rock
lithification
process of a sediment being convertend to a rock; it often involves compaction, descciation, cementation, and recrystallization
lithophile
an element that tends to concentratein silicates rather than in metals or sulfides
lode deposit
an ore deposit comprising many small veins
lower polarizer
a fixed polarizing lens located in the substage of a polarizing light microscope
luminescence
the emission of energy of a different wavelength froma mineral or other substance that has been stimulated by an external energy source of some wavelength(s)
luster
the reflection of light from the surface of something, described by its quality and intensity
macroscopic property
a mineral property seen or measure in a hand specimen
magma
naturally occuring molten rock materal
major element
an element that is a key and essential part of a mineral (see also minor element or trace element)
malleable
a term used to describe the tenacity of mienrals that are capable of being hammered into shapes
mammilary
having a breastlike appearance
Mannebach twin
an uncommon tiwn law in feldspar
marble
aa metamorphic rock containing primarily clacite or dolomite
marl
a calcareous rock containig significat amounts of clay and other detrital material
mass number
symbolized by (A), the totaly number of protons and neutrons in an atom
massive
a term describing a mineral or mineral aggregate lacking in internal structure or other distinguishable physical characteristics
matrix
small or fine-grained material that encloses larger grains or crystals
mechanical weathering
type of weathering involving the physical decomposition or breakdwon of minerals and rock to produce smaller pieces
melatope
the trace of the optic axis (uniaxial mineral) or the optic axes (biaxial mineral) in an interference figure; thepoint where the isogyres cross in a uniaxial interference figure; the points on the isogyres closest to the center of a Bxa or Bxo interference figure
Mesodesmic
describing a crystal in which the strength of all bonds from a cation to its coordinating anions is equal to exactly one-half the charge of the anions
metabasite
a metamorphosed mafic rock
metal (element)
a general term often applied to any element that ionizes easily to become a cation; alternatively used to mean any of a class of elements that, when in pure form, usually have the shiny surface, and are good conductors of heat an electricity
metal (native element)
native elements of metallic character; pricipally gold, silver, copper and platinum
metallic bond
an ideal chemical bond in which electrons are highly delocalized and free to move from one atom to another
metallic luster
a mineral luster caracterized by brightness and shininess and the ability to reflect light
metamorphic
an adjective pertaining to the process of metmorphism
metamorphic facies
a range of pressure-temperature conditions characterizsed by one or more specific mineral assemblages
metamorphic grade
the degree of metamorphism; generally equivalent to the temperature of metamorphism
metamorphism
mineralogical or textural changes in rocks in response to changes in physical or chemical conditions
metapelite
a metamorpic rock equivalent in composition to a clay-rich sediment
metapsammite
a metamorpich rock equivalent in composition to a clay-rich sediment
metasomatism
a change in rock composition due to the movement of pore fluids associated with metamorphism
metastable
(thermodynamics) adjective describing a mmineral or mineral assemblage that is not undergoing change ut does not have the minumum possible Gibbs free energy
metastable equilibrium
equilibrium not representative of the minimal possible Gibbs energy of a system; a chemical system at metastable equilibrium is not reacting but may eventually do so to attain stable equilibrium
micaceous
having the properties of a mica, the ability to be split into thin sheets
micrite
fine-grianed microcrystalline calcite; the term is sometimes used to refer to a chemical sedimentary rock composed of microcrystalline calcite
microcrystalline
having crystals that can only be seen with the aid of a microscope
microscopie property
a mienral property not generally seen or measured without a microscope
migmatite
a mixed rock composed of differend color hands, often associated with partial melting under high-grade metamorphic conditions
Miller index (indices)
numbers used to describe the orientation of a plane with respect to crystal axes; Miller indices are generally enclosed in parentheses
mineral
naturally occuring and crystalline substances of fixed or limited composition
mineral class
a broad category of minerals generally based on commonality of anions or anionic compleses; for exmaple., carbonates and sulfates are mineral classes
mineral formula
an expression that uses chemical symbols, parentheses, and subsrcipts to show the composition of a mineral
mineral group
a group of minerals within a class that are distinguished by common properties
mineralogy
the study of minerals, their formation, occurrence, properites, composition and classification
minor element
an element that substitutes for a major element in a mineral, generaly present at the 1-5% level (see also major element or trace element)
mirror plane
a basic symmetry operator across which a mirror image is created
miscbility gap
a compositional range in a solution series that is not stable as a single phase; a compositional range where unmixing occurs
miscibility
the ability of two or more phases to mix to produce one solid phase
Mississippie Valley-type deposit
an epigenetic ore deposit hosted by carbonate rocksl typically, a source of lead and zinc
mode (igneous rock)
the mineral composition of a rock; generally expresed in volume %
Moh's hardness scale
a relative scale of 1-10, based on reference minerals, that can be ued to describe a mineral's hardness
mole
the quantity in grams of an element or compound that equals the molecular weight of the substance; one mole of a substance contains Avogadro's number(6.022/10^23) of atoms/molecules of that substance
monochromatic
a term describing radiation consisting of one wavelength
monoclinic
of or related to the monoclinic crystal system
monoclinic (system)
a crystal system characterized by lattic symmetry 2/m and containing point groups with symmetry no great than 2/m; four cell parameters (a, b, c, ? ) are needed to describe the shape and size of monoclinic unit cell
monomineralic
containing only one mineral
monovalent
an ion having a charge of +/- 1
Monzonite
an intrusive igneous rock of intermediate compostion containing approximately equal amoutns of plagioclase and K-feldspar, minor quartz, clinopyroxene, biotite, and hornblende may be present
mother lode
an ore body that is the source for ore mienrals found in a placer
motif
a pattern that is repeated by symmetry
mud
unconsolidated sediment composed of clay and silt
mudstone
general term for a fine-grained clastic sedimentary rock composed of clay or silt; sometimes used only for such rocks if they are not foliated
native element
an element that occurs naturally as a mineral
natural
a product of nature, not of humans or human activities
nesosilicates
silicate minerals characterized by individual SiO4 tetrahedra linked by bonding to common cations (see also island silicates and isolated tetrahedral silicates)
network silicates
silicate minerals characterized by SiO4 tetrahedra joining to form three-dimensional networks ( see also tectosilicates and framework silicates)
neutron
a subatomic particle of neutral charge, generally found in atomic nuclei, that has about the same mass as a proton
noble gas
any of the generally unreactive elements (such as Ne, Ar, or Kr) in the 18th group of the Periodic Table of the Elements (see also inert gas)
noncrystalline
having a random atomic structure (see also amorphous)
nonmetal (native element)
native element minerals composed of nonmetallic elemets; principally sulfur, graphite, and diamond
nonmetallic (element)
elements that do not possess the propoerties of a metal. Nonmetallic elements generally ionize easily to become anions, have a nonmetallic luster, and are poor conductors of heat and electricity when pure
nonmetallic (luster)
a mineral luster that is not metallic (see also admantine, vitreous , resinous, silky, pearly, and greasy)
nonopaque (mineral)
a mineral that transmits light in thin section
nonprimitive
used to describe a unit cell containing more than one lattice point
nonspecial angle
an angle unrelated to angles btween symmetry elements (see also general angle)
nonprimitive
used to describe a unit cell containing more than one lattice point
nonspecial angle
an angle unrelated to angles between symmetry elements (see also general angle)
normalization
the process of converting a mineral analysis to a chemical formula
nuclei
plural of nucleus; the central parts of atoms consisting of protons, or of combinations of protons, neutrons, and other particles
numerical aperture
a number describing the size of the cone of light that can enter a lens
O ray
see ordinary ray
obsidian
volcanic glass produced by the rapid cooling of a magma
obtuse bisectrix
the direction bisecting the obtuse angle between the optic axes of a biaxial crystal; perpendicular to the acute bisectrix
obtuse bisectix figure (Bxo)
the biaxial interference figure seen when looking down the obtuse bisectrix
octahedral (cleavage)
a term used to describe four cleavages that produce octahedral cleavage fragments; for example, fluorite has octahedral cleavage
octahedral (coordination)
the bonding of an ion to six others arranged so that connecting their center forms an octahedron
ooctahedron
a cubic from [111] of eight faces, each an equilateral triangle; a from of crystal class 4/m32/m
ocular
a lens in an eyepiece of a microscope
oppalescence
the play of colors seen in some minerals that resembles that of opal
opaque
the inability to transmit light or to be seen through
open form
a form that, by itself, cannot enclose three-dimensional space
operation (symmetry)
an operation that repeats a motif, crystal face, or other entity in a symmetrical pattern
operatory (symmetry)
any symmetry element element that repeats a motif crystal face or other entity in a symmetrical pattern; rotation axis, mirror plane, inversion center, rotoinversion axis, translation, glide plane, or screw axis
optic axis
a direction through a crystal along which no double refraction occurs
optic axis figure
the interference figure seen when looking down an optic axis
optic normal
the direction perpendicular to the optic plane of a biaxial mineral, corresponding to the y-axis
optic normal interference figure
the interference figure obtained when looking down a optic normal
optic plane
the plane containing the optic axes of a biaxial crystal
optic sign
either + or - , describing the relationship between indices of refraction. In uniaxial positive (+) crystals; in uniaxial negative (-) crystal; in biaxial positive (+) crystals, ? is closer in value to ? than to ?; in biaxial negative (-) crystals, ? is closer in value to ? than to ?
order of diffraction
the value of n in Bragg's law; the number of cycles a diffracted beam lags behind an adjacent beam with which it is in phase
ordinary ray
in a uniaxial crystal, the ray of light that vibrates perpendicular to the optic axis and obeys Snell law
ore
anything that can be taken from the ground and sold for a profit
ore deposit
an economical concentration of ore mienrals
ore grade
the concentration of ore minerals or elements in ore rock
ore mineral
a mienral, usually metallic, that is economically desirable
organic
a compound contianing carbon bonded to hydrogen as an essential and major component
orthogonal
perpendicular
orthonet
a two-dimensional lattice characterized by two translations of different magnitudes at 90 degrees to each other
orthopyroxene
orthorhombic pyroxene subgroup dominated by end members enstatite and ferrosilite
orthorhombic
of or related to the orthorhombic crystal system
orthorhombic (system)
a crystal system characterized by lattice symmetry 2/m2/m2/m, and containing point group with symmetry no greater than 2/m2/m2/m, and three cell parameters (a,b,c) are needed to describe the shape and size of an orthorhombic unit cell
orthoscopic (illumination)
illumination caused by light rays all traveling parallel to the tube of polarizing light microscope
orthosilicates
obsolete (see also isolated tetrahedral silicates)
out-of-phase
the condition in which the peaks, and valleys, of two waves do not match in time and space
oxidation
the process of an atom losing one or more electrons through chemical reaction
oxide
compound of oxygen with another element or radical
oxidize
describes an element that has lost one or more electrons
paired tetrahedral silicates
silicate minerals characterized by SiO4 tetrahedra joined to form pairs (see also sorosilicates)
parallel extinction
extinction condition in which the principal cleavage or length of a crystal is parallel to the crosshair of a polarizing light microscope
paramagnetism
having a small magnetic susceptibility and being weakly attracted by a magnet
parent isotope
the initial radioactive member of a radioactive decay series
partial crystallization
separation of a crystallizing magma into parts by the successive crystallization of different minerals (see also fractional crystallization)
partial melting
melting of only some of the mienrals in a highgrade metamorphic
parting
breaking of a mineral along a plane of weakness; generally cause by twinning or deformation
Pauling's rules
five empirical rules, first tabulated by Linus Pauling, describing common structural and bonding features of ionic structures
pearly
a type of luster that appears iridescent, similar to pearls or some seashells
pedion
an open form consisting of one crystal face unrelated to any other by symmetry
pegmatite
an exceptionally coarse grained igneous rock; generally formed by crystallization of water-rich magmas
pelite
a rock with composition equivalent to a clay-rich sediment
penetration twin
a twin in which two individual crystals, sharing a common volume of atoms, appear to penetrate or grow through each other
pericline twin
a common twin law in triclinic feldspars; K-feldsapr that have both albite and pericline twins develop the (microscopic) scotch-plaid twinning characteristic of microcline
peridotite
a general term for an intrusive igneous rock of highly mafic composition; typically composed of olivine (+/-) other mafic minerals and minor plagioclase
period (of elements)
elements that occupy the same row in the Periodic Table of the Elements
periodic chart
also called the periodic table; a table in which the chemical elements are arranged in order of their atomic numbers and grouped in columns based on atomic structure
petrogenesis
the branch of petrology dealing with the origin and formation of rock
petrographic microscope
a microscope that uses polarizing light for observation and analysis of minerals in grain mounts or in thin sections (see also polarizing light microscope)
petrography
the branch of petrology dealing with the description and classification of rocks
phaneritic
having mineral grains visible without a microscope
phase diagram
any of a number of different types of diagrams used to depict mineral compositions or stability of various phases in a system; the axes are usually temperature, pressure, or composition
phase rule
a consequence of the laws of thermodynamics: for any chemical system in equilibrium, the number of chemical components plus two is equivalent to the number of stable phases plus the number of degrees of freedom: C+2=P+F (see also Gibbs phase rule)
phenocryst
the relatively large, conspicuous crystals in a porphyritic rock
phosphate (mineral)
group of minerals characterized by (PO4)3-, in their formulas
phosphate (radical)
the (PO4)3-, anionic group
phosphorescence
a type of luminescence in response to exposure to ultraviolet light, x-ray, or cathode ray that continues after the exposure ceases
phosphorite
a chemical sedimentary rock composed primarily of phosphate mienrals, typically varieties of apatite
phyllite
a foliated metamorphic rock, lacking in schistosity, having a sparkly or silky sheen due to the presence of fine-grained micas
phyllosilicates
silicate minerals containing SiO4 tetrahedra joined to form sheets; includes micas and clays (see also layer silicates and sheet silicates)
piezoelectric
having the ability to develop a small amount of electrical potential when strained
pinacoid
an open crystal form compised of two parallel faces
pipe
an igneous body with a more or less round cross section formed as a magma ascends rapidly to the Earth's surface
pisolitic
a term describing crystals that are very small spheres
pisolitic
a term describing crystals that are very small spheres
placer
a sedimentary mineral deposit, often fluvial, formed by the concentraion of heavy minerals due to gravitational forces
Planck's law
an equation that relates the energy (E) of an electromagnetic wave to its frequency (v):E=hv, where h is Planck's constant
plane defect
a kind of defect that occurs along the boundary plane of two regions of a crystal or between two grains
plane polarized
a term describing a moving wave, perhaps light, that is constrained to vibrate in one plane
plaster of Paris
a white calcium sulfate-based plaster that is more hydrated than anhydrate but less hydrated than gypsum
platy (cleavage)
a cleavege that allows a crystal to be broken into plates
platy (crystal)
appearing to be platelike, thin in one dimension compared with the other two (see also tabular and lamellar)
play of colors
the separation of white light into visible individual colors when it interacts with a mineral; often leading to changes in color as a mineral is turn (see also schiller)
pleochroism
the property of an anisotropic crystal to absorb different wavelengths, and thus to have different color, depending on orientation; most easily seen by rotating the stage of a polarizing light microscope while viewing an anisotropic crystal in thin section under plane polarized light
plumose
a term describing an aggregate of crystals having a feathery appearance
plutonic rock
an igneous rock that crystallizes at depth in the earth (see also intrusive rock)
point defect
a defect that occurs at one point in a crystal structure
point group
one of the 32 possible symmetry groups to which a crystal can belong; translation-free equivalent of space groups (see also crystal classes)
polarized (ions)
a term describing an ion with uneven electon distributation so that it does not behave as an ionic sphere in a crystal structure
polarized (wave)
a term describing a moving wave, perhaps light, that is not free to vibrate in all directions
polarizing light microscope
a microscope that uses polarizing light for observation and anlysis of minerals in grainmounts or in thin section (see also petrographic microscope)
pole
a perpendicular to a face on a crystal
polychromatic
radiation containing multiple wavelengths (see also monochromatic)
polyhedron
a three-dimensional geometric figure having four or more faces
polychromatic
radiation containing multiple wavelengths (see also monchromatic)
polyhedron
a three-dimensional geometric figure having four or more faces
polymer
a chemical unit formed by the tight linking of individual molecules
polymerization
the connecting of polyhedra or other structural units chains, sheets, or networks by sharing or atoms
polymorphs
minerals that have identical compositions but different crystal structures; for example, calcite and aragonite are polymorphs
polysynthetic twin
repeated twinning of three or more individuals according to the same twin law and in a parallel manner, porducing a twinned grain composed of many thin parallel sheetlike twin domains
porcelain
a special type of high-quality white ceramic
polymorphs
minerals that have identical compositions but different crystal structures; for example, calcite and aragonite are polymorphs
polysynethetic twin
repeated twining of three of more individuals according to the same twin law and in a parallel manner, producing a twinned grain composed of many thin parallel sheetlike twin domains
porphyroblast
a large mineral crystal, produced by metamorphism, in a finer-grained matrix
porphyry (igneous rock)
a rock containing relatviely large crystals (phenocrysts) in a fine-grained ground mass that may be crystalline or glassy
porphyry (ore deposit)
an ore deposit in which the ore is concentrayed in closely spaced small veins and neilets
Portland cement
the most common kind of cement; composed of a mixture of lime, silica, alumina, and iron oxides
powder diffraction
diffraction of X rays by a powdered sample
powder diffraction file (PDF)
the x-ray powder diffraction reference file used by m ost mineralogists
Precambrian shield
an ancient geological terrane that has been stable for a long time; typically in the central area (craton) of major continents
precious metals
gold, silver, platinum, and sometimes other platinum group elements
precipitate
to form solid material from material dissolved in a liquid; precipitated material generally but not always settles to the bottom of the liquid
primary mienral
a mineral formed at the same time as its host rock (see also secondary mineral)
primitive
describing a unit cell containing in total one lattice point; typically unit cells are chosen so that a primitive unit cell contains one-eighth of a lattice point at each corner
principal axis
the most prominent or unique crystal axis in crystal or the most prominent or unique rotational axis of symmetry in a crystal; generally they coincide
principle of parsimony (Pauling's rule 5)
the number of different components in a crystal tends to be small
prism
a crystal form characterized by two or more crystal faces parallel to a common direction
prismatic (cleavage)
a term used to describe multiple cleavages all parallel to a common direction in acrystal
prismatic (crystal)
having the appearance of a prism or prisms; appearing as a long crystal with parallel sides
prograde reactions
reactions that take place in response to an increase in temperature
prism
a crystal form characterised by two or more crystal faces parallel to a common direction
prismatic (cleavage)
a term used used to describe multiple cleavages all parallel to a common direction in a crystal
prismatic (crystal)
having the appearance of a prism or prisms; appearing as a long crystal with parallel sides
prograde metamorphism
metamorphism in response to increasing temperature
progressive metamorphism
metamorphism that proceeds by steps from low grade to high grade
proper rotation axis
a rotation axis of symmetry that does not involve inversion
proton
a subatomic particle, generally found in the nuclei of atoms, having the smallest amount of possitive electric charge occurring in nature
psammite
a rock equivalent in composition to a sandstone or feldspathic sandstone with minor amounts of clay
psuedohexagonal
symmetry that appears to be present but, with better measurement or observation, would be found to be lacking
pseudosymmetry
symmetry that appears to be present but, with better measurement or observation, would be found to be lacking
pycnometer
a small bottle with a tight-fitting stopper that is used to determine specific gravity
pyramid
an open crystal form of 3, 4, 6, 8, or 12 nonparallel faces that meet at a point
pyramidal cleavage
cleavage that gives cleaved crystals a pyramid shape
pyritohedron
a cubic crystal form, consisting of 12 irregular pentagonal facesl a form of crystal class 23 or 2/m3
pyroelectric
having the ability to develop a small amount of electrical potential when heated
pyroxenite
an ultramafic intrusive rock composed primarily of pyroxene with lesser amounts of olivine, biottite, or hornblende
quartz plate
an accessory plate for polarizing light microscopes that is composed of quartz of known optical orientation
quartz wedge
an elongate wedge of clear quartz of known optical orientation that may be inserted in a polarizing light microscope tube to analyze a crystal's optical properties
quartzite
a hard but unmetamorphosed sandstone or the metamorphic equivalent
quartzose
containing quartz as a primary component
radiating
emananting from a common point (see also divergent)
radical
a chemical group that has acquired an elctrical charge; orten surrounded by parentheses in mineral formulas
radioactivity
the spontaneous decay of atoms of certain isotopes into new isotopes, accompanied by the emission of high energy particles
radioisotope
an isotope that is the product of radioactive decay
radius ratio principle (Pauling's rule 1)
cation-anion distances are equal to the sum of their effective ionic radii, and cation coordination numbers are determined by the ratio of cation and anion radii
rare earth elements
elements (such as Ce, Pr, and Nd) with atomic numbers 58 through 71 and valence electrons in 4f orbitals (see also lanthanide elements)
recrystallization
formation of new crystals from preexisting material; the new crystals need not be the same species or composition as the material form which they from
recrystallize
to form new crystalline mineral grains in a rock, generally by metamorphism
reduce
said of an element; to gain one or more electrons
reduction
the process of an atom gaining one or more electrons through chemical reaction
reentrant angle
an angle between two crystal faces that points or is directed inward toward the center of the crystal; usually associated with twins
reflected light microscopy
microscopic examination using a light source that reflects form the surface of a sample; reflected light microscopy is useful for identifying opaque minerals in thin section
reflection (light)
coherent scattering of energy by atoms in a two-dimensional surgace
reflection (symmetry)
a term describing the operation that relates two crystal faces or other entities across a mirror plane
refraction
the deflection of a ray, perhaps light, due to its passage from one medium to another of fdifferent ray velocity
refractive index
the ratio off the velocity of light in a vacuum to the velocity of light in a given medium (see also index of refraction)
refractive index oil
a liquid of known index of refraction
refractometer
a device for determining the index of refraction of a crystal or other material
regional metamorphism
metamorphism affecting a large region; caused by pressure related to depth in the Earth and temperature related to geothermal gradient (see also burla metamorphism)
regular polyhedron
a coordinating polyhedron in which all cation-anion bond lengths are equal
relief
the apparent topography of a crystal or crystals seen under a microscope
reniform
having a kidney-shaped appearance
reserves
ore that has been identified and that could be extracted at a profit
residual (phase)
the remaining liquid, or phases that crystallize from such a liquid, after a magma has mostly solidified
residual (mineral)
a mineral that has been concentrated in place by weathering and leaching of rock
reserves
ore that has been identified and that could be extracted at a profit
residuum
insoluble material remaining after intense weather
resinous
a term used to describe mineral lusters that have the appearance of resin
reinstate
insoluble material produced by chemical weathering; the term is also used in a general sense to refer to any sedimentary material of low solubility
retardation
the distance that one wave lags behind another; specifically the distnace that the fast ray lags behind the slow ray upon emergence form a crystal
reticulated
crystals that have a latticelike appearance
retrograde metamorphism
metamorphismn that takes place in response to decreasing temperature
retrograde reactions
metamorphic reactions that take place in response to decreasing temperature
rhomb
a parallelogram having equal length sides and interior angles at 60 to 120
rhombohedral (point groups)
any of the point groups that include the rhombohedral from (3, 32, 32m)
rhombohedral plane lattice
a two-dimensional lattice characterized by two translations of equal magnitude at 60 degrees to each other (see also hexanet)
rhombohedron
a closed form that creates a parallelepiped with six identical rhomb-shaped races
rhyolite
an extrusive igneous rock of silicic composition containing 10%-50% quartz and K-feldspar as the major feldspar: plagioclase, biotite, and hornblende may be present (see also granite)
Rietveld method
a method of making crystal structure analyses based on powder diffraction data
tetragonal packing
the planar arrangement of spheres of identical size in a square pattern; each sphere is surrounded by eight others
tetrahedral (coordination)
the bonding of an ion to four others arranged so that connecting their centers forms a tetrahedron
tetrahedron
a geometric solid bonded by four equilateral traingles; specifically refers to a crystal form of the cubic system having four equilateral triangular faces
tetrahedron (silica)
a tetrahedral arrangement of Si4+ ad O2- ions having an overall composition and charge of SiO4 (2-),
tetravalent
an ion having a charge of +/- 4
thermodynamics
the branch of physics and physical chemisty that deals with the relationships between heat and other forms of energy, and of the conversion of one into the other
thermoluminescence
a type of luminescence caused by heating a mineral
thin section
a thin piece of rock glued on a glass slide and uniformly ground to a thickness of about 0.03 mm
tie line
a line connecting two mineral compoistions on a phase diagram; time lines sohw possible mineral assemblages
till
unsorted and unstratified glacial deposits
tonalite
an intrusive igneous rock of silicic composition in which the only major feldspar is plagioclase; bitotite and hornblende are typically present
trace element
an element that is not essential in a mineral but that is found in very small quantities is in its structure or absorbed on its surface (see also major element and minor element)
trachyte
an extrusive igneous rock of intermediate composition in which the amount of K-feldspar exceeds the amount of plagioclase; quartz, biotite, and hornblende may be present
transition element
an element from the fourth and thirteenth group of the PEriodic Table of the Elements and characterized by valence electrons in d-orbitals (see also transition metals)
transition metal
see transition element
translating
moving in one direction by a fixed increment
translation
a shift in position without rotation
translucent
the ability to transmit light without being transparent
transmitteed light microscopy
microscopic examiniation using light that passes through a crystal before reaching the eye; the standar kind of microscopy used by petrologists
transparent
the ability to be seen through; to transmit light with little loss in intensity
trapezohedron
a crystal form of 6, 8, or 12 faces, each a trapezium
travertine
a type of limestone formed by rapid precipitation of calcite, often but not necessarily associated with hot springs
triangular )coordination)
coordination of an ion to only three others
triclinic
of or related to the triclinic system
triclinic (system)
a crystal system characterized by lattice symmetry ? and containing point groups with symmetry no greater than?; six cell parameters, are needed to describe the shpae and size of triclinic unit cell
trigonal (system)
a subsystem of the hexahonal system containing all point groups lacking a 6-fold of ?-fold axis of symmetry
trioctahedral
describing a layered mineral structure in which three of three available octahgedral sites are occupied
trisoctahedron
a cubic form of 24 faces, each of which is an isosceles triangle; a form of crystal class 432, 2/m3 or 4/m32/m
trivalent
an ion having a charge of +/- 3
tumble
to polish a gem in a revolving box or barrel
twin
an intergrowth of two or more single crystals of the same mineral that share common atoms, typically along planes
twin lamellae
thin parallel individual twin domains that are part of a polysynthetic twin
twin law
a definition of a twin relationship in a mineral or mineral group, specifying the twin axis, center, or plane, defining the composition surface or plane if possible, and giving the type of twin
twin plane
a plane that separates two twin domains
twinning
the development of intergrowths of two or more single crystals of the same mineral that share common atoms, typically along planes
ultramafic
a general adjective referring to igneous rocks rich in magnesium and iron and containing primarily magic minerals
ultraviolet light
electromagnetic radiation with wavelengths slightly less than visible light
uneven fraction
a fracture that produces rough and irregular surfaces (see also irregular fracture)
uniaxial
a term describing a crystal that has only one optic axis; such crystals belong to the tetragonal or hexgonal crystal systems
unit cell
parallelepiped defined by three noncopolanar unit translations in a lattice; all crystals may be thought of as a collection of unit cells
unit cell parameters
the dimensions and angles that characterize a unit cell shape; typically symbolized by -------
univariant line
a line on a phase diagram; generally representing a reaction and having one degree of freedom
unmixing
the separation of an initially homogeneous solid, liquid, or gas phase into two or more of differnt compositions
unpolarized
a term describing light or any other wave that is free to vibrate in any direction
unstable (thermodynamics)
adjcetive describing a chemical system that does not have the minimum possible Gibbs energy; an unstable chemical system will react to obtain metastable or stable equilibrium if slightly perturbed
unstable isotope
a radioactive isotope of an element (see also radioisotope)
upper polarizer
a polarizing filter that may be inserted in the tube of a polarizng light microscope in order to view a sample undercrossed polars (see also analyzer
vacancy
a site in a mineral structure that is vacant but capable of holding an atom or ion under some circumstances
valence
the charge of an ion
valence electron
the outermost electrons of an atomt hat contribute most to the atom's bonding
Van der Waals bond
a weak type of electrostatic bond, generally insignifcant in minerals, created by brief fluctuations in the balance of positive and negative charges. Important in talc and graphite
vapor
used in a general sense to refer to a liquid, gas, or supercritical fluid; also used to refer to any gaseous phase emanating from a liquid or a solid
variety
a division of a mineral species based on particular physical characteristics such as color; for example chalcedony is avariety of quartz
Verneuil technique
a technique for synthesizing gems that involves melting powder and allowing it to accumulate and crystallize on a boule
vesicle
a cavity in a lava formed by a gas bubble trapped during cooling of the lava
viscosity
the thickness, or internal resistance to flow, of a liquid
vitreous
a type of luster resembling that of glass
volatile
a chemical material such as water or carbon dioxide, in a magma or rock, that may concentrate as a gas or vapor
volcanic rock
an igneous rock that crystallizes at or very near the Earth's surface (see also extrusive rock)
wave front
the front, or leading edge, of multiple in-phase waves traveling in the same direction
weathering
alteration of a rock by surface agnests; for example, water, wind, sun
Weisseberg camera
an instrument for recording single crystal diffraction patterns on film
white light
light composed of a spectrum of different wavelengths
whiteschist
a very high pressure-temperature metamorphic rock containing white micas and talc
x-radiation
electromagnetic wave with wavelength much shorter than visible light, on the order of 0.1 to 100A
x ray
electromagnetic wave with wavelength much shorter than visible light, on the order of 0.1 to 100A (see also x-radiation)
x-ray defraction
the apparent bending or channeling of x rays when they pass through a crystal structure
x ray fluoresncence
fluorescence of x rays caused by an incident x-ray beam striking a sample
xenolith
a rock inclusion picked up by a magma and present after the magma has solidified
Zeolite (facies)
the lowest pressure-temperature metamorphic facies; characterized by zeolites and other very low-grade minerals
zone (compositional)
an area in a crystal of distinct chemical composition
zone (metamorphic)
a region in a metamorphic terrane that is characterized by a specific mineral or mineral assemblage
zone axis
a line parallel to multiple crystal faces in a crystal
zoned
a term describing a crystal that has compositional zonation
zoning
variation in the composition of a crystal, typicall from core to margin (see also compositional zoning)