Orthoclase

Orthoclase is a member of the feldspar group (like plagioclase) and is a framework silicate. Orthoclase, also known as alkali feldspar or K-feldspar, is one end-member of a solid solution between orthoclase and albite.

Orthoclase is found in silica-rich igneous rocks such as granite, and in high grade metamorphic rocks.

Chemical composition - KAlSi 3O 8 Hardness - 6 Specific gravity - 2.6 Transparency - Translucent to opaque (rarely transparent) Colour - Pinkish white, off-white, yellow, or shades of red, orange to brown Streak - White Lustre - Vitreous Cleavage/fracture - Perfect in two directions, seldom twinned / hackly, conchoidal Crystal habit/mode of occurrence - Prismatic, tabular