Altisite

Altisite (IMA symbol: Ati ) is an exceedingly rare alkaline titanium aluminosilicate chloride mineral with formula Na3K6Ti2Al2Si8O26Cl3, from alkaline pegmatites. It is named after its composition (ALuminium, TItanium, and SIlicon).

The mineral crystallizes in the monoclinic crystal system with space group C2/m.