Sphene.
Reading edition
Sphene or titanite is also a brittle mineral, 5 to 5.5 in hardness; specific gravity, 3.4 to 3.56; transparent, doubly refractive; lustre, adamantine to resinous; colors, brown, gray, yellow, green, black, and colorless; and composition:
Silica 31
Titanium oxide 41
Lime 27
Ferrous oxide 1
When transparent in colorless, greenish, or yellow colors, this mineral presents an appearance like the fire opal.
Sphene is found in Switzerland, the Urals, Tyrol, Finland, Wales, Ireland, Germany, Canada, and the United States.