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Lecture 14 Systematic Description of Minerals 1. Mineral Classifications
Principally by dominant anion or anionic group Secondarily by internal mineral structure
Native ElementNative ElementSulfides (S)Sulfides (S)Sulfosalts (SbSulfosalts (Sb22SS33))Oxides (O)Oxides (O)Hydroxides (OH)Hydroxides (OH)Halides (Cl, F, Br, I)Halides (Cl, F, Br, I)Carbonates (COCarbonates (CO33))Sulfates (SOSulfates (SO44))Phosphates (POPhosphates (PO44))Nitrates, Borates, Tungstates, Molybdates, Arsenates, Vanadates...Nitrates, Borates, Tungstates, Molybdates, Arsenates, Vanadates...
SilicatesSilicates NesosilicatesNesosilicates SorosilicatesSorosilicates CyclosilicatesCyclosilicates InosilicatesInosilicates PhyllosilicatesPhyllosilicates TectosilicatesTectosilicates
Minerals for term paper
electronics
Native Elements and Sulfides
are frequently the targets of mining companies
Native Elements Metals – Gold, Silver, Copper,
Platinum, Palladium, Osmium, Iridium, Iron, Fe-nickel
Semi-metals – Arsenic, Bismuth, Antimony
Non-metals – Sulfur, Diamond, Graphite
Native Metals
metallic bonding dense, cubic close packing (“CCP”) properties: soft, malleable, ductile, sectile, good heat and electrical
conductors Melting points: low-Au, Ag, Cu
AuAu AgAg CuCu PtPt
Native Non-metalsSulfurSulfur DiamondDiamond GraphiteGraphite
SS88 ring molecules ring molecules bonded by weakbonded by weakvan der Waals van der Waals forcesforces
CC66 ring molecules ring molecules bonded by weakbonded by weakvan der Waals van der Waals forces; good forces; good electrical electrical conductivityconductivity
StrongStrongCovalentCovalentBondsBonds
Synthetic (industrial) DiamondsSynthetic (industrial) Diamonds
Native Element Occurrences
GoldGold – Hydrothermal fluids related to magmatism, especially late – Hydrothermal fluids related to magmatism, especially late fractionation; commonly occurs in veins of quartz and pyrite; may form fractionation; commonly occurs in veins of quartz and pyrite; may form detrital grains to produce placer deposits; Rarely occurs alloyed with detrital grains to produce placer deposits; Rarely occurs alloyed with other elements.other elements.
SilverSilver – Hydrothermal ore deposits rich in sulfides, arsenides, and – Hydrothermal ore deposits rich in sulfides, arsenides, and bismuthides; also commonly associated native copper.bismuthides; also commonly associated native copper.
Copper – Sulfide-poor hydrothermal ore deposits or secondary Copper – Sulfide-poor hydrothermal ore deposits or secondary oxidation of Cu-sulfide minerals; most abundant occurrence is the oxidation of Cu-sulfide minerals; most abundant occurrence is the native copper deposits of the Keweenawan Peninsula of Upper native copper deposits of the Keweenawan Peninsula of Upper Michigan where it occurs in lava flows and interflow conglomerates. Michigan where it occurs in lava flows and interflow conglomerates.
Native Element Occurrences
Platinum – Occurs as primary deposits in mafic intrusions and as Platinum – Occurs as primary deposits in mafic intrusions and as secondary placer deposits.secondary placer deposits.
Diamond – Occurs in mantle-derived Kimberlite pipes with other high Diamond – Occurs in mantle-derived Kimberlite pipes with other high temperature/high pressure minerals. Needs a subduction zone to temperature/high pressure minerals. Needs a subduction zone to pressurize ocean floor carbon, the a rising plume to hit the right depth pressurize ocean floor carbon, the a rising plume to hit the right depth in the subduction zone. That’s why they are rare.in the subduction zone. That’s why they are rare.
Sulfur – Precipitates near volcanic vents from volcanic gasses and Sulfur – Precipitates near volcanic vents from volcanic gasses and secondarily by oxidation of sulfide minerals. secondarily by oxidation of sulfide minerals.
Sulfides and Sulfosalts Most common ore source of metals XmSn
As (arsenic) may substitute for S giving rise to sulfarsenides, and arsenides
X= Fe, Cu, Zn, Pb, Ni, Co, Hg, Mo Magmatic and hydrothermal origin Sulfosalts, As, Sb, and Bi take the place
of metals (X)
Sulfide StabilityReducing to Oxidizing, Acidic to Basic Environments
Cu-HCu-H22O-OO-O22-S-CO-S-CO22 phase diagram phase diagramat 25°C and 1 atm pressureat 25°C and 1 atm pressure
Eh-pH diagrams are used for reactions that occur from aqueous solutions at low pressures. The voltage across a galvanic cell and the pH determine which mineral precipitates in a laboratory vessel containing all needed elements. These atmospheric pressure conditions model the formation of many major ores
High Temperature Low Pressure Sulfide formation at MORs
Cu-Fe Sulfide Minerals
PyPy
PoPo
CpCp
BnBn
CcCc
DgDg
CvCv
Other Common Sulfide Minerals
Galena PbS - dense, cubic cleavage
may contain substantial silver
Sphalerite (Zn,Fe)S – submetallic black to resinous yellow, brown lusterYellow streak
Pentlandite (Fe,Ni)9S8 – yellow-bronze; in magmatic ores
Cinnabar HgS – vermilion-red color, dense
Molybdenite MoS2 – silver metallic sheets
PtPt
GalenaGalena
Zn>>FeZn>>Fe
Zn>FeZn>Fe
ZnZn
Arsenosulfides, Arsenides and Sulfosalts
Cobaltite (Co,Fe)AsSCobaltite (Co,Fe)AsS – silver white metallic – silver white metallic
Arsenopyrite FeAsSArsenopyrite FeAsS – silver white metallic – silver white metallic
Realgar AsS Realgar AsS (red)(red) - Orpiment As - Orpiment As22SS33 (yellow)(yellow)
Stibnite SbStibnite Sb22SS33 silver-gray prisms silver-gray prisms
Enargite CuEnargite Cu33AsSAsS44 – striated metallic columns – striated metallic columns and blades – a sulfosaltand blades – a sulfosalt
Skutterudite (Co,Ni)AsSkutterudite (Co,Ni)As33 silver-gray cubes silver-gray cubes
(Antimony sulfide)