Chromite. The Great Dyke, Zimbabwe
Euhedral chromite crystals (grey) are fractured, some fractures are along a poorly defined cleavage (bottom centre) and are accompanied by incipient alteration (higher reflectance areas, centre right). Silicate (dark grey) forms the matrix to the chromite and replaces it (bottom right).
Polished block, plane polarized light, x 160, air