Microcline

Chemical Formula : KAlSi₃O₈
Hardness : 6
Cleavage : Two, good
Luster : Vitreous
Color : White, cream, light blue
Streak : White
Density : 2.56
Diagnostic Features and Trivia : Microcline is comonly found in pegmatites since it forms at a lower temperature than Orthoclase. Often its distinctive blue color will give it away.
Crystal System and Habit : Triclinic; common crystals are short prismsatic, somewhat flattened parallel to {010}.
Twinning : Commonly polysynthetic on both albite and pericline laws, giving characteristic grating and gridiron structures.
Polymorphs : Orthoclase
Index of Refraction : alpha=1.514-1.516; beta=1.518-1.519; gamma=1.521-1.522