What is "acuminite"

n. (context mineral English) A mineral composed of strontium, aluminium, fluorine, oxygen, and hydrogen.

Acuminite is a rare halide mineral of with chemical formula: Sr Al F( OH)·( HO). Its name comes from the Latin word acumen, meaning "spear point". Its Mohs scale rating is 3.5.

Acumenite has only been described from its type locality of the cryolite deposit in Ivigtut, Greenland.