Tourmaline (Achroite, Dravite, Rubellite, Indicolite, Verdelite, Siberite)
Four Arrows (MC81.JRG)
By Jeff R. Graham
Copyright 2002
91.8% Light Return
Angles for R.I. = 1.62
49 facets + 8 facets on girdle = 57
4-fold, mirror-image symmetry
96 index
L/W = 1.000 T/W = 0.244 T/L = 0.244
P/W = 0.445 C/W = 0.203
H/W = (P+C)/W+0.02 = 0.668
P/H = 0.666 C/H = 0.304
Vol./W^3 = 0.260
Addition # 7 – This is nice in about any material, I often use it for cutting dark stones. Cut in refractive indexes 1.62 to 2.14 with no changes. This makes good earrings, easy to set and are low profile so they wear well.
Random – Cosine – ISO
Detailed faceting instructions by Jeff Graham available at The Rock Peddler
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.
