ORTHOCLASE, ORGAN MOUNTAINS NEW MEXICO USA (small cabinet)

Orthoclase, also known as orthoclase feldspar with the chemical formula KAlSi3O8, is a significant tectosilicate mineral that contributes to the formation of igneous rocks. Its name derives from the Ancient Greek term meaning "straight fracture," reflecting the mineral's characteristic cleavage planes that intersect at right angles. As a member of the alkali feldspar group, it is commonly referred to as potassium feldspar or K-spar. Notably, the gemstone moonstone is primarily composed of orthoclase.