Common Forms/Occurrences: Common K-feldspar of pegmatites and hydrothermal veins; Prominent in granites Useful Identification Test: Demonstrates "tartan" twinning Chemical formula: KAlSi3O8 Crystal System: Translucent prisms with subparallel exsolution lamellae Colour: Orange, brown, white, green, or pink Streak: White Lustre: Nonmetallic (M) Cleavage: Excellent in two directions at nearly 90° Fracture: Uneven; Brittle Hardness: 6 Hardness Search: six Specific Gravity: 2.5 - 2.6
