Mineralogy

Front 1

What is a mineral?

Back 1

A mineral is a naturally occurring solid with a long-rangecrystalline structure and a definite, but not necessarily fixed,chemical composition.

Front 2

Why petroleum and oil are not considered minerals?

Back 2

• Petroleum and coal are not minerals because they do not have a definitechemical formula or an ordered atomic arrangement

Front 3

What is a mineraloid?

Back 3

• Mineraloids are mineral-like materials that lack a longrangecrystalline structure.• Examples: amorphous solids such as volcanic glass (left photobelow, obsidian) and microcrystalline quartz (right photobelow; this variety is opal).

Front 4

What is a metamict?

Back 4

The termmetamict is used to describe minerals that have disruptedstructures due to radioactive decay - metamict mineralsare formally classified as mineraloids.

Front 5

What are the two types of symmetry in crystallography?

Back 5

• In crystallography, we deal with two types of symmetry:

- Translational symmetry - repetition of a motif througha volume of space

- Point symmetry - repetition of a motif around a pointor a collection of points (such as a line)

Front 6

What is a,b and c in crystallography?

Back 6

• The dimensions (lengths) of thetranslations in the a, b and c directionsfor the minerals are also called a, band c; these dimensions are given inthe textbook (for example see themineral olivine, p. 338).

Front 7

What is alfa, beta and gama?

Back 7

• The symbols alfa, beta and gama are used todescribe the angles between thecrystallographic axes: is the angle between b & c is the angle between a & c is the angle between a & b

Front 8

What are the bravais lettices?

Back 8

• The five possible plane latticesmay be translated into the thirddimension producing 14 possiblespace lattices known as theBravais lattices (Figure 2.10).

Front 9

What are the crystal systems? How many? How many unit cells are possible?

Back 9

• The 14 possible Bravais latticescan be sorted by their unit cellshape into 6 crystal systems (Fig.2.10). For the hexagonal system,note there are 2 unit cell shapes,so there are a total of 7 possible“unit cell” shapes.

Front 10

WHat are the names of the crystal systems and the relationship among the axis.

Back 10

Front 11

Is there only one shape for each crystal system?

Back 11

• For each crystal system, various crystal shapes are possible,but their internal structure always matches the unit cell of thatsystem.

Front 12

What is point symmetry?

Back 12

• Point symmetry deals with how a motif is repeated around a point or acollection of points (i.e. a line).

Front 13

What are the operations in the point symmetry?

Back 13

• There are three simple point symmetry operations: reflection rotation inversion

Front 14

What is the inversion in the point symmetry?

Back 14

Inversion• Inversion symmetry exists ifan imaginary line can be drawnfrom a crystal feature throughthe middle of a crystal(inversion center) thatintersects an identical featureequidistant on the op

Front 15

What is space groups?

Back 15

• Space groups represent the combination of point symmetryand translational symmetry.

Front 16

What are the other symmetry operations?

Back 16

1. Glides: produced by acombination of a translationand a reflection

Front 17

What does the Steno's Law say?

Back 17

the angle between equivalentfaces on crystals of the same mineral is always the same.

Front 18

What is the Law of Bravais?

Back 18

Common crystal faces are parallel to latticeplanes that have a high lattice node density.

Front 19

what is Law of Haűy?

Back 19

Crystal faces make simple rational interceptson crystal axes.

• What does that mean? Faces intersect the crystal axes atdistances from the axes origin that are in simple ratios.• So an individual crystal face can be uniquely identified byspecifying the set of rational intersection points at which that faceintersects the crystallographic axes.• Mineralogists use a system called Miller Indices for this.

Front 20

What are miller indices?

Back 20

• Miller Indices: a shorthand system to describe theorientation of crystal faces.• Miller indices are written (h,k,l); using parentheses.

Front 21

WHat is a crystal zone?

Back 21

• A crystal zone is a collection ofcrystal faces that are all parallelto a common line - the zone axis.• A zone is noted using [squarebrackets] around the zone axis.

Front 22

What is a crystal form?

Back 22

• A crystal form is a collection of equivalent crystal faces related toeach other by the symmetry of the mineral. • Crystal forms are indicated by curly brackets {} around theMiller indices of the one of the faces that comprise the form.