Chemical Differences: Rutile and Ilmenite

        Titanium Dioxide helps to form crystaline structures in glaze melts. The most common materials added to glazes to introduce TiO2 are Titanium Dioxide itself, Rutile, and Ilmenite. Both Rutile and Ilmenite contain a significant amount of TiO2. However, Ilmenite contains more "contaminants" compared to Rutile. On a simplistic level, Ilmenite contains approximately 50% FeO whereas Rutile only contains about 10% Fe3O2. Both also contain other contaminants that are in minute levels.

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Rutile: 
Can be found in granular or powdered form. The varied size varies the mottling in the glaze. The most commonly produced colors by Rutile are tan and blue (seed of the glaze name "Rutile Blue"). The Titanium Dioxide in it can inhibit crystal formation (see Permafrost Base, Rutile Line Blend) and the iron in the material can help in fluxing the glaze at high levels. Rutile can also be used to soften the color producted by more potent colorants such as Chrome and Cobalt and variegate the both the texture and color in a glaze (see Satin Base Green).


Ilmenite:
Also can be found in granular or powdered form, however is more common in granular. Can be used in clay bodies or glazes to produce a speckled effect. Like Rutile, can seed Titania crystals in a glaze. The higher amounts of iron in the material can help to flux. Grains of Ilmenite in a glaze can bleed out at higher temperatures, forming dark blemishes. In combination with Rutile, Ilmenite can help to produce the characteristic Rutile streaking and mottling.