Description
Afghanite (Afghanite or Afghanita) (Na, Ca, K)8(Si, Al)12O24(SO4,Cl, CO3)3·H2O is a mineral of sodium, calcium, potassium, silicon, aluminum, oxygen, sulfur, chlorine, carbon, and hydrogen. It is named after Afghanistan. Its hardness on the Mohs scale is 5.5 to 6. The elements sodium and potassium are interchangeable, but always exist in the same ratio to the other components of the mineral. Chemically, afghanite is a sodium-potassium-calcium aluminosilicate with chlorine and sulfate ([SO4]2−) ions. It belongs to the tectosilicates. Afghanite is transparent and forms crystals with a vitreous luster; it also occurs in the form of rounded crystallites. The color varies between light and dark blue, and in thin slices it is colorless; the streak color is white. Afghanite was first discovered in the Ladjuar Medam lapis lazuli deposits near Sar-e-Sang in Afghanistan. These Ladjuar Medam deposits were already known in antiquity. In 1968, this mineral was described by Pierre Bariand, Fabien Cesbron, and Roger Giraud. They named it after the country where it was found.
