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Microcline (Var. Amazonite)
Lake George, Colorado
These two crystals measure 6.5cm x 5.5cm in height
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:The specimens shown above display albite epitaxial overgrowth.
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
Note: Specimen collected by Lance E. Kearns, 1970
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals