1) Triclinic mineral 
Tantite is a rare tantalum oxide mineral with formula: Ta2O5. Tantite forms transparent microscopic colorless triclinic - pedial crystals with an adamantine luster. It has a Mohs hardness of 7 and a high specific gravity of 8.45. Chemical analyses show minor inclusion (1.3%) of niobium oxide. It was first described in 1983 for an occurrence in a p...