Al₆(BO₃)₅(F,OH)₃

This sample of jeremejevite is displayed in the Smithsonian Museum of Natural History. Jeremejevite is a oxide mineral of aluminum with fluorine and boron (a borate). Its composition is Al₆(BO₃)₅(F,OH)₃. The sample at left is about 8 cm long and the gem is 3 carats. It is from Swakopmund, Namibia.