Black Ilmenite and “Titanium White”

The bright-white color that we see in everything from highway lines, donut icing, and tooth-paste to paint, paper, plastics, and ceramics comes mostly from titanium dioxide, the world’s most widely used pigment.

- STEVE VOYNICK

Titanium dioxide, better known as “titanium white,” originates, oddly enough, with the black mineral ilmenite.

Named for its type locality in the Ilmen Mountains of Russia’s southern Urals, ilmenite is iron titanium oxide (FeTiO3 ). An abundant mineral that crystallizes in the trigonal system, ilmenite usually occurs in massive or granular forms and occasionally as the tabular crystals sought by mineral collectors. Black, opaque, weakly magnetic, and exhibiting a metallic-to-submetallic luster, ilmenite has a Mohs hardness of 5.5-6.0 and a substantial specific gravity of 4.7-4.8.

As one of the first minerals to crystallize from solidifying magma, ilmenite’s density enables it to concentrate in layers at the bottom of magma chambers through the process of magmatic segregation. Solidification usually produces igneous masses with ilmenite-enriched layers. Then, as the host rock eventually weathers and erodes, the freed ilmenite particles concentrate in alluvial deposits. Placer miners know that the black sands in gold-pan and sluice concen-trates often consist largely of ilmenite.