ilmenite has a black streak; it is opaque, but in very thin scales sometimes transparent with a clove-brown colour.
Rutile and ilmenite both have high specific gravity and are little affected by weathering.
The principal titanium minerals are rutile (titanium oxide) and ilmenite (iron titanate).
ilmenite has sometimes been mistaken in the South African mines for carbonado.
Among the accessory minerals may be mentioned apatite, magnetite, ilmenite, picotite and garnet.