When Was Orthoclase Discovered?

It was first described by Ermenegildo Pini in 1781. The optical effect of adularescence in moonstone is typically due to adularia. The largest documented single crystal of orthoclase was found in the Ural mountains in Russia. It measured ~10×10×0.4 m and weighed ~100 tons.

Where is orthoclase found?

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.

What is orthoclase used for?

Orthoclase is used in the manufacture of glass and ceramics; occasionally, transparent crystals are cut as gems. Orthoclase is primarily important as a rock-forming mineral, however, and is abundant in alkali and acidic igneous rocks, in pegmatites, and in gneisses.