Demantoid Faceting / Facet Garnet Information


Demantoid (Garnet)

demantoid Barion cut - faceting styles“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
Cleavage: Imperfect
Fracture: Subconchoidal
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)

Design Links:
Tic Tac – Good for dark material
Smith Bar – Great for any material
Brilliant Pear – Nice in about anything

About the author
Jeff R. Graham
The late Jeff Graham was a prolific faceter, creator of many original faceting designs, and the author of several highly-regarded instructional faceting books such as Gram Faceting Designs.
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