A hard black spinel mineral, an iron (II)
chromium (III) mixed oxide (FeO.Cr2O3);
it is the only important ore of chromium.
Chromite separates from magma when igneous
rocks first form, occurring as octahedral crystals and as granular masses.
It is weakly magnetic and opaque. The vast majority of the world's chromite
is found in South Africa and Zimbabwe. Hardness 5.5, relative density 4.6.
Image source: Mineral Information Institute
AND PLANETARY SCIENCE