Lecture 17.06.ppt
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Transcript of Lecture 17.06.ppt
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Lecture 17 (11/27/2006)
Systematic Description of Minerals
Part 1:Native Elements and
Sulfides
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Mineral Classifications
Principally by dominant anion or anionic group
Secondarily by internal mineral structure
Native Element
Sulfides (S)Sulfosalts (AsS)Oxides (O)Hydroxides (OH)Halides (Cl, F, Br, I)
Carbonates (CO3)Sulfates (SO4)Phosphates (PO4)Nitrates, Borates, Tungstates, Molybdates, Arsenates, Vanadates..
Silicates
NesosilicatesSorosilicatesCyclosilicatesInosilicatesPhyllosilicates
Tectosilicates
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Native Elements
MetalsGold, Silver, Copper,Platinum, Palladium, Osmium,Iridium, Iron, Fe-nickel
Semi-metalsArsenic, Bismuth,Antimony
Non-metalsSulfur, Diamond,Graphite
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Native Metals metallic bonding
dense, cubic close packing
properties: soft, malleable, ductile, sectile, good heatand electrical conductors
variable melting points: low-Au, Ag, Cu; high-PGEs
Au Ag Cu Pt
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Native Non-metals
Sulfur Diamond Graphite
S8ring moleculesbonded by weakvan der Waalsforces
C6ring molecules
bonded by weakvan der Waalsforces; goodelectricalconductivity
StrongCovalentBonds
Synthetic (industrial) Diamonds
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Native Element OccurrencesGold Hydrothermal fluids related to magmatism; commonly occurs
in veins quartz and pyrite; may form detrital grains to produce placerdeposits; Rarely occurs alloyed with other elements.
Silver Hydrothermal ore deposits rich in sulfide, arsenides, andbismithides; also commonly associated native copper.
CopperSulfide-poor hydrothermal ore deposits or secondaryoxidation of Cu-sulfide minerals; most abundant occurrence is thenative copper deposits of the Keweenawan Peninsula of UpperMichigan where it occurs in lava flows and interflow conglomerates.
Platinum
Occurs as primary deposits in mafic intrusions and assecondary placer deposits.
DiamondOccurs in mantle-derived kimberlite pipes with other hightemperature/high pressure minerals
SulfurPrecipitates near volcanic vents from volcanic gasses andsecondarily by oxidation of sulfide minerals.
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Sulfides and Sulfosalts
Most common ore source of metals
XmSn
Asmay substitute for Sgiving rise tosulfarsenides, and arsenides X= Fe, Cu, Zn, Pb, Ni, Co, Hg, Mo
Magmatic and hydrothermal originSulfosalts, As, Sb, and Bi take the
place of metals (X)
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Sulfide StabilityReducing, Acidic
Environment
Cu-H2O-O2-S-CO2phase diagramat 25C and 1 atm pressure
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Cu-Fe Sulfide Minerals
Py
Po
Cp
Bn
Cc
Dg
Cv
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Other Common Sulfide Minerals
Galena PbS - dense, cubic cleavage
Sphalerite (Zn,Fe)S submetallicblack to resinous yellow, brown luster
Pentlandite (Fe,Ni)9S8 yellow-bronze; w/ Cp and Po in magmaticores
Cinnabar HgSvermilion-red color,dense
Molybdenite MoS2silver metallicsheets
Pt
Galena
Zn>>Fe
Zn>Fe
Zn
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Arsenosulfides, Arsenides and Sulfosalts
Cobaltite (Co,Fe)AsS
silver white metallic
Arsenopyrite FeAsSsilver white metallic
Realgar AsS (red)- Orpiment As2S3(yellow)
Stibnite Sb2S3 silver-gray prisms
Enargite Cu3AsS4striated metallic columns
and bladesa sulfosalt
Skutterudite (Co,Ni)As3 silver-gray cubes
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Next Lecture 11/29/06
Systematic Description of Minerals
Part 2:Oxides, Hydroxides Halides,Carbonates, Sulfates, and Phosphates
Read: Klein Parts of Chaps. 9 & 10