Ortoklass

Ortoklass is a term sometimes used in petrology to refer to orthoclase, a mineral belonging to the feldspar group. Orthoclase is a high-temperature polymorph of potassium feldspar, with the chemical formula KAlSi₃O₈. It crystallizes in the monoclinic crystal system. Its common occurrence is in felsic igneous rocks, such as granite and syenite. It can also be found in metamorphic rocks like gneiss and schist. In sedimentary rocks, orthoclase is often present as a detrital mineral, derived from the weathering of pre-existing igneous or metamorphic rocks.

The color of orthoclase can vary, but it is typically white, colorless, or pale pink. It has a Mohs hardness of 6, meaning it is moderately hard. The mineral exhibits two good cleavage directions, which intersect at nearly right angles. This characteristic cleavage is typical of feldspars. In geological contexts, orthoclase is an important indicator of the conditions under which rocks formed. Its presence suggests an alkaline magmatic environment and relatively high temperatures during crystallization. The term "ortoklass" itself is a less common variant and may arise from transliteration or regional nomenclature, but it fundamentally refers to this specific potassium feldspar mineral.