In ceramics this material is available in a variety of sizes. It can be used at a speckling agent in glazes, however it settles quickly because it has a high specific gravity. It can also be used as a speckling agent in bodies, try around 0.2% to start.
Glaze Variegation - Speckle
Granular rutile is popular as a specking agent. Start with 0.2%. This material is heavy and will settle in glaze with a thin slurry.
Yes, the granular and powdered grades are the same material. But grinding it is very difficult. Commercial ceramic grade powder is minus 325 mesh, the companies doing this obviously have very good grinding equipment. They also have patience because even in this efficient porcelain ball mill, 90 minutes was only enough to get 50% to minus 325 mesh! The color of the powder is a good indication of its quality, the finer the grind the lighter will be the tan coloration.
Out Bound Links
Illmenite, Ferrous Titanate, Iron Titanate
In Bound Links
FERROSO-FERRIC OXIDE, FEROSIC OXIDE
Illmenite Granular, Granular Illmenite, Granular Iron Titanate