Astrophyllite from Eveslogchorr Mountain, Khibiny Massif, Kola Peninsula, Russia

The mineral astrophyllite / astrophylite is a potassium-sodium-iron-manganese-titanium-silicate with the chemical formula K2Na (Fe2 +, Mn) 7Ti2Si8O26 (OH) 4. It belongs to the inosilicates. The golden-yellow, bronze-yellow or brown to brown-red astrophyllite has a diamond to pearl sheen, a yellow-brown stripe color and a perfect cleavage according to the crystal plane [001]. The average density is 3.34 and the hardness is 3 to 3.5. The crystal system is triclene and the radioactivity of the mineral is barely measurable. The gamma ray value according to the American Petroleum Institute is 85.21. The name of the mineral astrophyllite is derived from the Greek words astro ("star") and fylon ("leaf"). The mineral astrophyllite mainly occurs in zirconium-containing syenites. The type location is the Langesund Fjord, near Brevik, Norway.