Mineral Identification (With Pictures)

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Orthoclase (K-rich feldspar)
2 cleavages, almost 90 degrees
Hardness x6
Vitreous luster (resembles glass)
Common in granite
Often pink but may be white or gray
(Non-metallic)

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Plagioclase (Na-rich feldspar)
2 cleavages, almost 90 degrees
Hardness 6
Striations Vitreous luster (resembles glass)
Found in light colored igneous rocks
(Non-metallic)

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Crystal Quartz (SiO2)
Hexagonal (6 sided prism), pointed ends
Hardness 7
No cleavage, conchoidal fracture
One of the most common minerals
Vitreous luster (resembles glass)
(Non-metallic)

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Chalcedony (SiO2)
Type of quartz
Hardness 7
No cleavage, conchoidal fracture
Compact microcrystalline quartz
Waxy luster
(Non-metallic)

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Olivine
Green to yellow
No cleavage - Commonly granular masses
Hardness 6 1/2 to 7
Streak white
Coarse grained
Commonly found in gabbro and basalt
(Non-metallic)

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Halite (NaCl)
Clear to white
3 directions of cleavage at 90 degrees
Salty taste
Hardness 2 1/2
(Non-metallic)

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Calcite (CaCo3)
Fizzes with acid
Clear - white to yellow
3 directions of cleavage - not at 90 degrees
Hardness 3
(Non-metallic)

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Gypsum Selenite
Clear to white
2 directions of cleavage
Hardness 2
(Non-metallic)

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Muscovite Mica
Clear to light yellow
1 direction of cleavage (breaks in thin sheets)
Vitreous luster (resembles glass)
Fluorescent
Hardness 4
(Non-metallic)

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Fluorite
White, yellowish, or purple
4 directions of cleavage
Vitreous luster (resembles glass)
Fluorescent
Hardness 4
(Non-metallic)

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Talc
Pale green to white
Soapy, greasy feel
Hardness 1
Foliated appearance
Formed by low grade metamorphism
(Non-metallic)

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Augite
Green to black
2 directions of cleavage at nearly 90 degrees
Hardness 5-6
Found in igneous rocks § Basalt Gabbro
(Non-metallic)

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Hornblende
Black, long columnar crystals
2 directions of cleavage at 60 degrees
Splintery appearance
Hardness 5-6
Common in igneous and metamorphic rocks
(Non-metallic)

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Plagioclase (Ca-rich feldspar)
Dark colored
2 directions of cleavage at almost 90o
Striations on some cleavage surfaces
Hardness 6
(Non-metallic)

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Almandine Garnet
Deep red
No cleavage, irregular fracture
12 sided crystals
Hardness 6.5-7.5
White streak
(Non-metallic)

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Grossular Garnet
Green, yellow, pink, purple, etc. colors
No cleavage, irregular fracture
12 sided crystals
Hardness 6.5-7.5
White streak
(Non-metallic)

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Smoky Quartz (SiO2)
Gray to black
No cleavage, Granular masses
Concoidal fracture
Vitreous luster
Hardness 7
(Non-metallic)

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Biotite Mica
Brown to black
1 direction of cleavage (flat)
Easy to break into thin flexible sheets
Hardness 2.5-3
Shiny, thin layers
(Non-metallic)

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Sphalerite (ZnS)
Yellow brown to black
Color resulting from variable iron content
6 directions of cleavage
Resinous luster
Hardness 3.5-4
White to yellow streak
Commonly associated with galena

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Oolitic Hematite
Brick red to red brown
Earthly luster
Oolitic (rounded granules)
Red streak

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Limonite
Yellow to yellow-brown to brown-black
Earthly luster
Yellow-brown streak
Hardness 5-5.5

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Graphite (C)
Gray to black
Marks paper easily, used as pencil "lead"
Hardness 1
Greasy feel

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Magnetite (Fe3O4)
Black, Magnetic
Hardness 6
Streak black
Well-shaped crystals and/or granular masses

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Pyrite (FeS2)
Brassy, "fools gold"
Hardness 6
Green-black streak
Crystallizes into cubes

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Chalcopyrite
Brass-yellow
Some iridescence
Hardness 3.5-4
Green-black streak
Most important ore of copper

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Galena (PbS)
Shiny gray
3 directions of cleavage
Hardness 3.5-4
Very dense and heavy

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Specular Hematite (Fe2O3)
Silver, black or red
Many tiny glittering flakes
Hardness 5-6
Red streak