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43 Cards in this Set
- Front
- Back
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What are the noble metals, and characteristics?
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Gold Au
Silver Ag PGE platinum group elemetns hard, high density high heat tolerance resistent to acids rare, costly to find and recover corrosion resistance |
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how much of all gold ever mined is still in use?
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85%
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Gold is often found with what other mineral in hydrothermal vein deposits?
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Gold and Quartz.
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how much of gold is held in banks?
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25%
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Gold uses
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Electronics - circuit boards, connectors, contacts
Non-corrosive = reliable, long-term electrical connections military/weapons and space bound electronics |
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How much of gold is hoarded? why?
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Gold Hoarding >80% of consumption
Viewed as an economic hedge against inflation and political instability |
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White Gold -
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alloyed w/ nickel, palladium or manganese
sometimes coated with rhodium |
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Gold resources
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Native gold - Au
Electrum - natural Au-Ag alloy Gold telluride minerals - AuTe2 |
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how is gold formed
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Hydrothermal fluids flowing through
fractured rock precipitated gold along with quartz "gold-quartz veins" |
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do we have gold deposits today?
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Hydrothermal vein deposits are mostly mined-out
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How are hydrothermal fluids mined?
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Hydrothermal fluids also deposit low-grade disseminated ores surrounding veins
Focus of current mining Economically mined using cyanide heap-leaching methods |
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Placer Deposits
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Sedimentary
deposits formed by erosion of uplifted outcrops of gold-quartz vein deposits |
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Surface outcrops
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and are
composed of loose sand, gravel, and cobbles |
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Placer Gold
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Dense gold particles are only be
transported downstream when water velocity is high |
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1849 California Gold Rush
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1848 - James Marshall discovered placer gold
at John Sutter's sawmill near Sacramento Placer’s were followed upstream to the “Mother Lode” - Mesozoic hydrothermal gold-quartz vein deposits in the Sierra Nevada Mnts Gold Rush brought more settlement of the western U.S. than any other single event |
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Hydraulic Mining
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uses water to
move sediment through sluices to separate gold 1850s --banned 184 because destructive, destroyed rivers. |
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Witwatersrand placers
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are lithified (hard) placer deposits - paleoplacer
Discovered in 1886 - 20x larger than any other gold district - South African Gold Rush |
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how much of gold production happened in the last 100 years?
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50% of global gold production in last 100 years
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Uniformitarianism -- gold
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Witwatersrand gold-uranium
paleo-placers are important evidence for the oxygen-poor nature of the Earth's early atmosphere. The nature of ore deposits through geologic time reflects the changing nature Earth's biota and atmosphere |
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what properties of gold make it useful in jewlery?
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malleable
chemically inert alloys easily |
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Karat
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purity in 24th 24 karat = 100% pure
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Global Au reserves
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15% in South Africa, 5% in U.S.
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Recycling Au provides ~
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50% of U.S. consumption
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underground gold mining: Underground, Surface, Dredging &
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Underground: Pneumatic drills and blasting
High-grade vein deposits Witwatersrand placers<-- deep , expensive Surface mining:Young placers Disseminated low-grade deposits 20 Dredging - scraping sediments from a lake or river bottom |
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Cyanide Heap Leaching
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Heaps of crushed ore placed on plastic mats
Sprayed with sodium cyanide (NaCN) solution Cyanide dissolves Au - "pregnant solution" Solution pumped over activated carbon absorbs the Au Carbon is soaked in acid - re-dissolves the Au Au is electroplated onto steel wool wool is smelted to make "dore" impure gold alloy Dore is refined to bars high purity Au -- CHEAP EASY |
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TF all US currency is backed wtih an equal amount of gold by the Federal Reserve Bank
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False, gold standard not effective.
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PGE Elements
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platinum
palladium RUTHENIUM RHODIUM OSMIUM IRIDIUM |
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PGE are typically used in cars for what purpose
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catalytic converter
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How much of gold for fashion?
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75%
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what similar properties of PGE
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corrosion resistant high temp tolerance
easily alloyed catalysts (speed chem reaction) |
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Porous ceramic
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high surface area
allows the catalytic PGE coating to quickly react with the exhaust gases |
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Demand for PGE?
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clean air act,better for environment in cars
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PGE other uses
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jewlery
Strong settings for gemstones Protective coating for Au, Ag More fashionable than "common" gold? |
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PGE Igneous deposits
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magmatic segregations:
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PGE Placer deposits
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from erosion of
igneous deposits (Ural Mts., Russia) mostly mined out and depleted |
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PGE Underground and Open Pit Mining
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Ore is crushed
Concentrated by flotation & density separation Smelted to make Cu-Ni matte (impure alloy) containing PGE PGE separated by selective leaching, extraction & precipitation |
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platinum was regarded as ____ by europeans explorers when they first encoutered it in Ecuador
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worthless
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Almost 50% of US PGE production is from
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recycled catalytic converters
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Rare Earth Elements: Lanthanides
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15 elements starting wth Lanthanum have similar properties.
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what are REE good for?
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super conductors (novel prize) conduct industry better than copper, but require low temps to work.
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TF the US has no significant are earth elements deposits
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False, mountain pass mine in CA
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REE market dominated by which country
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China
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we currently obtain most of our platinum group element consumption from which types of deposits?
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Heavy PGE bearing minerals found at the bottom of ancient magma chambers
placer -- nuggets flakes and grains of native PGE found mixed with stream deposited sediments. |
