Processed rutile ore (upgraded to 95%+ TiO2 by smelting). Available in a variety of sizes. It can be used at a speckling agent in glazes, however it settles quickly because of the high specific gravity. It can also be used as a speckling agent in bodies, try around 0.2% to start.
Possible to grind your own ceramic grade rutile?
Yes, the granular and powdered grades or pure rutile 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 tan it will be.
Colorant Metallic based materials that impart fired color to glazes and bodies.