Potassium feldspar

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

  • Orthoclase (endmember formula KAlSi3O8), 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)4O8
  • Adularia, a more ordered low-temperature variety of orthoclase or partially disordered microcline
  • Amazonite (sometimes called "Amazon stone"), a green variety of microcline