Coulsonite, FeV2O4 or FeO·V2O3, previously named and recognized from India, but only vaguely described, has been identified in magnetite-bearing rocks from the Buena Vista Hills east of Lovelock, Nevada. In polished section the mineral is bluish-gray in color with its powder varying between dark brown to black. H = 4.5 to 5. Coulsonite shows a mean reflectivity of 23.5 determined with a slit microphotometer using green light. Under crossed nicols coulsonite appears isotropic although occasionally it is weakly anisotropic. The mineral is isometric, space group Fd3m, with a = 8.297 Å, and 8 formula units per unit cell. G(meas.) = 5.17 to 5.20, and G(calc.) = 5.15.