Faceting Design Diagram: Double Dart – Tourmaline – Achroite, Dravite, Rubellite, Indicolite, Verdelite, Siberite


Tourmaline (Achroite, Dravite, Rubellite, Indicolite, Verdelite, Siberite)

Double Dart (TLINE64.JRG)
By Jeff R. Graham
Copyright 1998
88% Light Return
Angles for R.I. = 1.62
121 facets + 8 facets on girdle = 129
8-fold, mirror-image symmetry
96 index
L/W = 1.000 T/W = 0.503 T/L = 0.503
P/W = 0.410 C/W = 0.202
H/W = (P+C)/W+0.02 = 0.632
P/H = 0.649 C/H = 0.319
Vol./W^3 = 0.207

Addition # 3 – This should be cut in a larger stone, the size of the P6,P7 are small and cut very fast. Some of these tiers have no meets, they have to be cut carefully. It can be hard to line up, medium material, 1-16cts. Cut in refractive indexes 1.62 to 1.93 (93%) with no changes.


Random – Cosine – ISO

Detailed faceting instructions by Jeff Graham available at The Rock Peddler

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.