Sphene Faceting Information
Color: Brown, yellow, green, brownish-red
Moh’s Hardness: 5-5.5
Refractive Index: 1.995-2.05
Critical Angle: 30.17°
Specific Gravity: 3.52-3.54
Fracture: conchoidal, brittle
Heat Sensitivity: Moderate
Dichroic: Medium to strong
Birefringence (double refraction): Very strong (.105-.135)
Crystal Structure: Monoclinic
Treatments: Generally none
What I prefer to polishing with: Alumina oxide on tin or tin oxide on tin lap
Jeff’s Comments: Faceting grade material is not common and seldom very big. Orient the stone to avoid cleavage planes (twinning plan) on the table and use a fine lap for cutting. Some facets may take hand lapping to get them cut and polished. Finished stones are quite stunning.
Design Notes: About any Zircon design will work well.