What is "potassium feldspar"

n. (context mineralogy English) Any of several alkaline feldspars containing potassium aluminium silicate, KAlSi₃O₈

Potassium feldspar refers to a number of minerals falling in the feldspar group, and containing potassium:

• Orthoclase (endmember formula K Al Si O), an important tectosilicate mineral that forms igneous rock
• Microcline, chemically the same as orthoclase, but with a different crystalline structure
• Sanidine, the high temperature form of potassium feldspar (K,Na)(Si,Al)O
• Adularia, a more ordered low-temperature variety of orthoclase or partially disordered microcline
• Amazonite (sometimes called "Amazon stone"), a green variety of microcline