Lecture 17 (11/27/2006)
Systematic Description of Minerals
Part 1: Native Elements and
Sulfides
Mineral Classifications


Principally by dominant anion or anionic group
Secondarily by internal mineral structure
Silicates
Native Element
Nesosilicates
Sulfides (S)
Sorosilicates
Sulfosalts (AsS)
Cyclosilicates
Oxides (O)
Inosilicates
Hydroxides (OH)
Phyllosilicates
Halides (Cl, F, Br, I)
Tectosilicates
Carbonates (CO3)
Sulfates (SO4)
Phosphates (PO4)
Nitrates, Borates, Tungstates, Molybdates, Arsenates, Vanadates..
Native Elements
 Metals
– Gold, Silver, Copper,
Platinum, Palladium, Osmium,
Iridium, Iron, Fe-nickel
 Semi-metals
Antimony
 Non-metals
Graphite
– Arsenic, Bismuth,
– Sulfur, Diamond,
Native Metals




metallic bonding
dense, cubic close packing
properties: soft, malleable, ductile, sectile, good heat
and electrical conductors
variable melting points: low-Au, Ag, Cu; high-PGEs
Au
Ag
Cu
Pt
Native Non-metals
Sulfur
Diamond
Graphite
Strong
Covalent
Bonds
C6 ring molecules
bonded by weak
van der Waals
forces; good
electrical
conductivity
S8 ring molecules
bonded by weak
van der Waals
forces
Synthetic (industrial) Diamonds
Native Element Occurrences
Gold – Hydrothermal fluids related to magmatism; commonly occurs
in veins quartz and pyrite; may form detrital grains to produce placer
deposits; Rarely occurs alloyed with other elements.
Silver – Hydrothermal ore deposits rich in sulfide, arsenides, and
bismithides; also commonly associated native copper.
Copper – Sulfide-poor hydrothermal ore deposits or secondary
oxidation of Cu-sulfide minerals; most abundant occurrence is the
native copper deposits of the Keweenawan Peninsula of Upper
Michigan where it occurs in lava flows and interflow conglomerates.
Platinum – Occurs as primary deposits in mafic intrusions and as
secondary placer deposits.
Diamond – Occurs in mantle-derived kimberlite pipes with other high
temperature/high pressure minerals
Sulfur – Precipitates near volcanic vents from volcanic gasses and
secondarily by oxidation of sulfide minerals.
Sulfides and Sulfosalts
 Most
common ore source of metals
 XmSn
 As
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 Stability
Reducing, Acidic
Environment
Cu-H2O-O2-S-CO2 phase diagram
at 25°C and 1 atm pressure
Cu-Fe Sulfide Minerals
Py
Cv
Po
Dg
Cp
Cc
Bn
Other Common Sulfide Minerals
Galena
Zn
Zn>>Fe

Galena PbS - dense, cubic cleavage

Sphalerite (Zn,Fe)S – submetallic
black to resinous yellow, brown luster
Zn>Fe

Pentlandite (Fe,Ni)9S8 – yellow-
bronze; w/ Cp and Po in magmatic
ores
Pt

Cinnabar HgS – vermilion-red color,
dense

Molybdenite MoS2 – silver metallic
sheets
Arsenosulfides, Arsenides and Sulfosalts
Cobaltite (Co,Fe)AsS – silver white metallic
Arsenopyrite FeAsS – silver white metallic
Realgar AsS
(red)
- Orpiment As2S3
(yellow)
Skutterudite (Co,Ni)As3 silver-gray cubes
Stibnite Sb2S3 silver-gray prisms
Enargite Cu3AsS4 – striated metallic columns
and blades – a sulfosalt
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