Ilmenite also known as Ferrous Titanate or Iron Titanate
Like rutile, ilmenite is quite variable in nature. You can tell the difference between granular rutile and granular ilmenite by doing a smear test against an abrasive surface (i.e. an unglazed white tile). The rutile will be tan or brown, the ilmenite will be black or dark brown. Likewise, under a microscope the ilmenite will be an opaque black whereas the rutile crystals will be somewhat translucent or transparent.
Ilmenite can be used in small amounts (-1%) to produce dark brown specks in bodies and specialized glazes. It also is used in combination with rutile to develop characteristic rutile break glazes; it seeds crystals in titania glazes.