Rutile is used in many industries (e.g. welding rods, paint) and ceramic uses are minor in comparison (for this reason bags of rutile might have labels like "Welding Rod Titanate"). Rutile is often sourced by companies in the titania and zircon supply business. The are large reserves of rutile in the world and any supply shortages are thus related to other factors.
 
Rutile is available in light calcined ceramic grade powder (very fine particle size), dark uncalcined powder, and granular form. Either grade of powder can be ground very fine (e.g. 325 mesh). In glazes it is generally better to use the ceramic grade since the decomposition of raw rutile during firing can be a source of glaze imperfections like pinholing and bubbles (even larger amounts of the ceramic grade, e.g. 8%, can also cause problems).
 
Rutile produces many crystalline, speckling, streaking, and mottling effects in glazes during cooling in the kiln and has been used in all types of colored glazes to enhance the surface character. It is thus highly prized by potters, many attractive variegated glazes are made using it.