Idocrase / Vesuvianite
Color: Green to olive/green, yellow/green
Moh’s Hardness: 6.5
Refractive Index: 1.71
Critical Angle: 35.79°
Specific Gravity: 3.32-3.42
Cleavage: Imperfect
Fracture: Uneven, splintery
Dispersion: .019
Heat Sensitivity: Low
Dichroic: weak
Birefringence (double refraction): Weak (.005)
Crystal Structure: Tetragonal Cutting:
Treatments: Generally none
What I prefer to polishing with: Alumina oxide on a Tin lap
Jeff’s Comments: Idocrase is actually pretty rare… Most material is slightly sleepy/silky but it facets a very nice green stone for anybody’s gemstone collection. Vargas in faceting for Amateur says (p253)… “This material handles easily with care. Most rough is flawed, and flawless gems are small and rare.”
Design Notes: About any Tourmaline, Topaz designs will work well… I prefer checker boards because they help hide the silk.
Design Links: Cornered – This is great for clear rough if you have a piece that will work…
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.
