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Microcline (Var. Amazonite)
Lake George, Colorado
This specimen measures 10cm x 8cm
Microcline KAlSi3O8
Tectosilicate; potassium aluminum silicate, sometimes with considerable amounts of sodium
Color and Luster: White, pink, brown, gray, blue, green, colorless, yellowish; vitreous, streak white
Hardness: 6-6.5
Cleavage: Good, two directions at 90°
Fracture: Uneven
Crystals: Triclinic; predominantly as single crystals of rectangular or square cross section and as tabular crystals; twin crystals very common; also cleavage masses, granular, disseminated grains
Note: Orthoclase, sanadine, adularia, and microcline are the potash feldspars
Andularia is often called moonstone, with a transparent or opalescent appearance
Sanadine is glassy,
Microcline is white to pale yellow, rarely red, and when bright green or blue it is called amazonite
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals