Titanite

Titanite, or sphene (from the Greek sphenos (σφηνώ), meaning wedge), is a calcium titanium silicate mineral. Its chemical formula is CaTiSiO5. Iron and aluminium are sometimes found in it. Also sometimes found in it are rare earth metals including cerium and yttrium, and the actinide thorium.

 References 

 Other websites 

 Madagascar Sphene Properties, Occurrences and Geological data

Category:Titanium minerals
Category:Gemstones
Category:Nesosilicates