What is the X in X-mas?
one of three minerals composed of titanium dioxide (TiO2), the other two being rutile and brookite. It is found as hard, brilliant crystals of tetragonal symmetry and various colours in veins in igneous and metamorphic rocks and commonly in placer deposits of detritus. Notable vein deposits exist in many regions of the Alps; placer deposits are common in Minas Gerais and Bahia, Braz. Much anatase is formed by weathering of titanite, and it is itself altered to rutile; rutile paramorphs (replacements having the same outward shape) after anatase are common in the detrital deposits of Brazil and the Sanarka region of the Urals. For detailed physical properties, see oxide mineral (table)