Description
The mineral charoite is a hydrated potassium-calcium silicate with the chemical formula (K,Na)5(Ca,Ba,Sr)8Si6O15Si6O16(OH,F)·H2O. It belongs to the inosilicate family. Light brown, lilac, or purple charoite has a vitreous to pearlescent luster, a white streak color, and good cleavage according to unknown crystal faces. Its average density is 2.56 and its hardness is 5 to 6. The crystal system is monoclinic, and the mineral's radioactivity is barely measurable. Its gamma ray value, according to the American Petroleum Institute, is 154.18. The mineral's name is derived from the Chara River in Siberia. Charoite occurs in a syenite massif where limestone has been transformed by contact metamorphism at approximately 200–250 degrees Celsius. The type locality is the Murun Massif, Chara River area, Aldan Shield, southwestern Yakutia. Charoite occurs here along with dark green aegirine needles, yellow tenaksite, and greenish-white nepheline.
