Native Elements, Sulfides, Halides, Sulfates - Faculty web pages

Native Elements – occur in elemental state
Metals:
Gold group of periodic table: gold, silver, copper
• Similar chemical properties
• Inert
• Soft, malleable, ductile
• Excellent conductors of electricity and heat
• Low melting points
• High densities

Gold - Au
Silver - Ag
Copper - Cu

Native Elements - Non-metals
Sulfur – S
Orthorhombic, yellow
Poor conductor of heat
Burns easily
Absence of good cleavage
Graphite – C
Hexagonal, metallic luster
Greasy feel
1 direction of cleavage
H = 1-2

Native Elements - Non-metals
Polymorphs
Diamond - C
Isometric
Octahedral xstals
Strongly bonded structure
Each C atoms covalently
bonded to 4 C neighbors
Graphite – C
Hexagonal, metallic luster
Greasy feel
1 direction of cleavage
H = 1-2

Sulfides: Majority of ore minerals
Most opaque with distinctive colors and streaks
Galena - PbS
Isometric
Cubic xstals and cleavage
Metallic luster
High S.G. = 7.4-7.6
Occurrence:
1) hydrothermal veins;
2) Mississippi Valley deposits
Sphalerite - ZnS
Isometric, yellow to brown
Massive form also tetrahedrons,
cubes
Yellow streak; Zn ore
Occurrence:
1) veins in igneous rocks
2) Mississippi Valley deposits

Sulfides: Majority of ore minerals
Most opaque with distinctive colors and streaks
Pyrite – FeS 2 ; Isometric
Cubic xstals with striated faces; also pyritohedrons and octahedrons
Metallic luster; conchoidal fracture; Greenish-black streak
Most common and widespread sulfide mineral
Occurrence:
1) Accessory mineral in igneous, metamorphic and sed rocks
2) Mississippi Valley deposits
3) Other sulfide deposits

Sulfides: Majority of ore minerals
Most opaque with distinctive colors and streaks
Chalcopyrite – CuFeS 2 ; Tetragonal
Massive or tetragonal tetrahedron xstals
Metallic luster; brass yellow to iridescent; Greenish-black streak
Cu ore – most widely occurring
Occurrence:
1) Chief Cu mineral at Sudbury, Ont. and high T deposits
2) Mississippi Valley deposits
3) Cu-porphyry deposits

Sulfides: Majority of ore minerals
Most opaque with distinctive colors and streaks
Cinnabar – HgS; Hexagonal
Massive or fine granular; Hg ore
Vermillion red; scarlet streak
High S. G. = 8
Occurrence: few localities
Vein fillings near recent volcanic
rocks and hot springs
Molybdenite – MoS 2
Hexagonal; foliated or massive
1 direction of cleavage
Metallic luster; blue-gray color
S.G. = 4.6; similar to graphite
Occurrence: 1) hydrothermal
veins; 2) accessory in granites,
pegmatites: 3) contact metamorphic
deposits

Halides: Dominated by halogen ions, Cl, Br, F, I
High symmetry forms
Halite – NaCl; Isometric
Cubic xstals; transparent luster
Salty taste
H = 2.5; S. G. = 2.16
Occurrence: Evaporite occurring
in extensive beds and irregular
masses
Fluorite – CaF 2
Isometric; cubic xstals
Octahedral cleavage
Vitreous luster; color varies
H = 4; S.G. = 3.2
Occurrence: 1) hydrothermal
veins; 2) accessory mineral in
igneous rocks and pegmatites

Sulfates: contain SO 4
2-
Anhydrous
Anhydrite – CaSO 4
Orthorhombic; massive
H = 3; S. G. = 2.9
Vitreous luster; colorless to blue
or violet
Occurrence: associated w/salt
deposits; amygdules in basalt
Not common
Barite - BaSO 4
Orthorhombic; tabular habit
Barite roses
Vitreous luster; colorless -white
H = 3; S.G. = 4.5
Occurrence: common; hydrothermal
veins
Used as heavy mud in oil/gas
industry

Sulfates: contain SO 4
2-
Hydrous
Selenite
Gypsum – CaSO 4 2 H 2 O
Monoclinic; most common sulfate: xstals tabular or diamondshaped
H = 2; S. G. = 2.3; scratches w/fingernail
Vitreous luster; colorless to white; 3 unequal cleavages not at
90°; varieties – satin spar, selenite, alabaster
Occurrence: common in sed rocks; evaporite deposits
Used in sheetrock and plaster of Paris