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26 Cards in this Set
- Front
- Back
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What is a gemstone or gem?
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1. material used for decoration
2. relatively rare 3. hard 4. tough. 5. withstand corrosion fron skin |
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How many gems are considered relatively common?
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about 200
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"Collector gems"
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- soft
- fragile - kept in paper - traded in "fold of paper" |
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Gemmology
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Field of study that encompasses the identification, evaluation of quality, valuation and science of gems.
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Native element
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naturally occurring material whose chemical formula has only 1 chemical element. ex. diamond
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Mineral
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naturally occurring inorganic chemical compound
ex. Quartz: SiO2, Olivine: (Mg, Fe)2SiO4 |
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What is the gem name of olivine?
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peridot
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what Is the gem name of corundum?
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ruby or sapphire
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Biomineral
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chemical compound secreted by a living organism
example: CaCO3 generated by mollusk - aragonite, calcite |
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synthetic chemical compounds
synthetic monoelemental compound |
both made in laboratory
ex: ruby, sapphire, emerald, opal, cubic zirconium, yttrium aluminum garnet ex. diamond |
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Cost depends on:
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1. weight
2. quality |
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Essential qualities of a gem
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1. beauty
2. rarity (supply/demand, fashion, scarcity) 3. durability (day-to-day wear and tear) |
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what are the 3 most abundant elements in earths crust?
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aluminum, oxygen, and silicon
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cleavage
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occurs along a well defined plane of weak atomic bonding splitting the stone in 2
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polymorph
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mineral which differ in shape but have same composition
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cubic cleavage
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breakage among mutually orthogonal directions gives rise to small cubic shaped cleavage fragments
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muscovite cleavage
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occurs along layers that separate sheets bonded together by weak bonds
ex. phyllosilicate mineral --> basal cleavage ex. topaz |
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rhombohedral cleavage
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cleavage is parallel to rhombohedral faces ex. calcite
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octahedral cleavage
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exhibited by cubic minerals (diamond), not natural crystal surfaces
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Quality of cleavages
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perfect (diamond, topaz)
imperfect distinct good fair poor (corrundum, quartz) |
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Difficulty of cleavage
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easy (bad)
hard difficult |
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durability
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combination of hardness and cleavage, helps sustain shock against breakage
ex. nephrite jade |
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fracture
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when mineral breaks along certain directions not related to atomic bonding
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conchoidal
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shell-like fracture, with series of scalloped rings ex. quartz garnets
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hackly or splintery
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form of long fibrous splinters
ex. nephrite, jade, ivory |
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smooth or even
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not perfectly flat but shows no signs of significant irregularities
ex. rough diamonds |
