Grossmanite

Grossmanite is a very rare mineral of the pyroxene group,^[1] with formula CaTi³⁺AlSiO₆.^[2] It is the titanium-dominant member. Grossmanite is unique in being a mineral with trivalent titanium, a feature shared with tistarite, Ti₂O₃.^[3] Titanium in minerals is almost exclusively tetravalent. Grossmanite stands for titanium-analogue of davisite, esseneite and kushiroite – other members of the pyroxene group. Both grossmanite and tistarite come from the famous Allende meteorite.^[1]