Demantoid Garnet Faceting
- “Demantoid Garnet,” fancy Barion barrel cut, 0.71 cts, Madagascar. © Dan Stair Custom Gemstones. Used with permission.
Color: Green, Emerald Green
Moh’s Hardness: 6.5-7
Refractive Index: 1.88-1.89
Critical Angle: 32.13°
Specific Gravity: 3.82-3.85
Heat Sensitivity: Yes
Birefringence (double refraction): 0.057
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron
Treatments: Generally none
What I prefer to polishing with: Alumina oxide with a tin lap (scored).
Jeff’s Comments: Typically has horse hair type inclusions/needles, seldom over a gram rough (usually 1-3 carats). Rough is hard to find…
Design Notes: Design choice is limited by the small size and inclusions, I generally cut a simple checker board that is as deep as I can cut from the rough.
Melanite – Opaque black variety (Andradite)
Topazolite – lemon/yellow variety of Andradite (similar to Mali Garnets)