Occurs in well shaped prismatic and tabular crystals.
Crystals often form penetration and repeated twins , and are frequently striated .
Also occurs massive , grainy , and as rounded, waterworn stones. The cleavage angle is about 90 Fracture Conchoidal to uneven Tenacity Brittle Varieties Adularia - White or colorless, transparent to translucent variety of Orthoclase and Sanidine . Moonstone - Adularia displaying adularescence . Noble Orthoclase - Transparent, yellow variety of Orthoclase. Microcline and Sanidine are sometimes incorrectly classified as a variety of Orthoclase.