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