Sphalerite Facet / Faceting Information


Sphalerite

Color: Green, brown, yellow, red, orange and colorless
Moh’s Hardness: 3.5-4
Refractive Index: 2.268-2.371
Critical Angle: 26.26°
Specific Gravity: 4.08-4.10
Cleavage: Perfect in 6 directions
Fracture: Uneven, brittle
Dispersion: .156
Heat Sensitivity: Moderate
Birefringence (double refraction): None
Crystal Structure: Cubic, isometric

Treatments: Generally none

What I prefer to polishing with: Alumina oxide on tin or wax lap

Jeff’s Comments: Faceting grade material is not common and seldom very big. Orient the stone to avoid cleavage planes 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…

Gram Faceting Archive of Information
This edited version of an article by the late Jeff Graham is part of a special archived informational series from Gram Faceting. Used with permission.