Described by Breithaupt in 1823, its name comes from the Greek Greek “orthos” meaning “straight fracture“, because it has the characteristic to cleave in two orthogonal planes. Named at the beginning orthoclase, orthose, its french name, was given lately by René Just Haüy.
In its white variety adularia, which name comes from the Latin word “Adula” which was the name of Mount St Gothard in Switzerland where it was commonly found, it is a constituent of the moonstone. The adularia is actually a microperthite, a result of the demixing of microscopic platelets of albite in the orthoclase during the cooling of the mixture of orthoclase and albite.
The adularescence phenomenon, which is the apparition of bluish reflets, is due to the interference created by these micro-plates of albite in the orthoclase forming a real grating diffraction.
The sanidine is a light color variety (colorless, light brown), discovered by Nose in Germany in 1808, its name comes from the Greek “Sanis” which means “ in small plates “ and “Idos” for “ to see “, summarizing the appearance of its crystals.
It is the standard hardness number 6 on the Mohs scale of hardness which goes from 1 to 10 .