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30 Cards in this Set
- Front
- Back
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Gem that forms directly within igneous rock |
Moonstone
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Some of the biggest and best crystals in nature come from special igneous rocks called
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Pegmatites
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Pegmatites are most often associated with the granites that make up ______________
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Mountain cores
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3 gems that form from gasses and hot fluids released from molten rock
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Topaz. Red beryl. Tourmaline
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3 gems produced by metamorphism
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Ruby. Garnet. Spinel
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What do gem deposits found in sedimentary rocks have in common?
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The action of water
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What is the most visible sign of igneous activity?
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A volcano
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Alkali-Basalt is often associated with gem quality________
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Sapphire
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Which 2 minerals make up the bulk of granite
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Quartz and feldspar
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Which deposit type produces more kinds of gems than any other?
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Pegmatites
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What does this depict
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Pegmatite formation
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What crucial role does super heated water play in gem formation
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It can transfer minerals in solution and redeposit them in veins to form gems
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The worlds most important pegmatite source is
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Minas Gerais in Brazil
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3 Gems found in hydrothermal veins
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Rich purple amethyst, imperial topaz and the worlds finest emeralds
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This depicts
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Hydrothermal gem formation
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Water that's pressurized and heated to high temps can carry more minerals in solutions than cooler waters T/F
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True
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2 key localities for hydrothermal gems
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Colombian emerald mines of Muzo and ouro preto Brazil
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Ouro Preto, Brazil has the only known deposits of
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Imperial topaz
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The finest opal is mined in
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Australia
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Why must opal and emerald be mined from primary deposits
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They're too fragile to survive water transport
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Where would you mine gems from a primary deposit
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Directly from the original rock
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Where would you mine gems from a secondary deposit
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In river gravel
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Which gem can be found in eluvial but not alluvial deposits
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Emeralds (too delicate)
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Which gem can form directly in lava
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Moonstone
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Which 2 gems can crystallize in volcanic rocks from the gasses that the cooling magma releases
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Topaz. Rare red beryl
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Heated limestone converts into
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Marble
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Kunzite is most often found in association with
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Tourmaline and beryl in pegmatite
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Myanmar's famous Mogok ruby deposits were formed by
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Regional metamorphism
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Pegmatite gems are rich in volatile elements like
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Beryllium. Boron. Lithium
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Most of the gems in Tanzania's Zumba River Valley are found in
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Placer deposits
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