a direction perpendicular to both the a and the b crystal axes. Twinning is uncertain. The mineral has a Mohs hardness of 5 1/2 to 6, between apatite and feldspar. This is the same hardness as anatase and a little less than that of rutile (6 to 6 1/2). The specific gravity is 4.08 to 4.18, between that of anatase at 3.9 and rutile at 4.2.

Occurrence and associations