Grossmanite is a very rare mineral of the pyroxene group, with formula CaTi<sup>3+</sup>AlSiO<sub>6</sub>. It is the titanium-dominant member. Grossmanite is unique in being a mineral with trivalent titanium, a feature shared with tistarite, Ti<sub>2</sub>O<sub>3</sub>. Titanium in minerals is almost exclusively tetravalent. Grossmanite stands for titanium-analogue of davisite, esseneite and kushiroite â other members of the pyroxene group. Both grossmanite and tistarite come from the famous Allende meteorite.