Corundum

Pit 298, Ilmen Natural Reserve, Ilmenskie Mountains, Chelyabinsk Oblast, Ural Federal District  Russia

Specimen size: 4.8 × 4.6 × 3.4 cm = 1.89” × 1.81” × 1.34”
Main crystal size: 4 × 3.6 cm = 1.57” × 1.42”