Origin of sphene
Examples from the Web for sphene
Most gem-stones are harder than quartz, though precious opal, turquoise, moonstone and sphene are inferior to it in hardness.
Sphene, biotite and iron oxides are the other common constituents, but these rocks show much variety of composition and structure.
The rarer stones, sphene and epidote, likewise exhibit this property markedly.A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public|Frank Bertram Wade
The iron oxides, originally ilmenite, are usually altered to sphene.
Reddish grains of sphene or of garnet are occasionally visible.