Name: from Greek: straight fracture, because its two cleavage planes are at right angles to each other.
Clades:
Alkali feldspars;
Tectosilicates;
Silicates;
Lapidae.
Dutch: Orthoklaas; Adulaar.
Chemical: KAlSi3O8.
Color: colorless; greeny, grey-yellow, white, rose; streak white.
Hardness: 6.
Specific gravity: 2,56 kg/dm3
Lustre: glassy.
Crystal structure: Monocline.
MineralogyOrthoclase, or orthoclase feldspar.
It forms igneous rock.
The gem known as moonstone is largely composed of orthoclase.