Orthoclase Facet / Faceting Information

A great informational article about tips on Orthoclase Faceting. Covers Orthoclase Faceting related issues, news, research, and much more helpful details.


Orthoclase Facet / Faceting Information

Orthoclase (Feldspar)

Shiller Sunstone carvineg/orthoclase

Color: Colorless, champagne to yellow
Moh's Hardness: 6-6.5
Refractive Index: 1.52-1.568
Critical Angle: 41.14°
Specific Gravity: 2.56-2.62
Cleavage: Perfect in 3 directions, can be a problem when cutting
Fracture: Uneven, somewhat brittle
Dispersion: .012
Heat Sensitivity: Moderate in my experience
Dichroism: Weak
Birefringence (double refraction): Weak to medium (.005-.01)
Crystal Structure: Monoclinic

Treatments: Generally none

What I prefer to polishing with: Cerium oxide with a Spectra Ultralap.

Jeff's Comments: Cuts and polishes easily, use a medium fine lap like a 600 grit for roughing in because a coarse lap can sometimes aggravate cleavage. Cleavage can be a problem, sharp corners have a tendency to chip out sometimes during cutting.

Design Notes: About any Quartz design will work well… I prefer a deeper design and often cut Barions.

Design Links: Tzar - High dome will help improve color and sparkle

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.

Never Stop Learning

When you join the IGS community, you get trusted diamond & gemstone information when you need it.

Become a Member

Get Gemology Insights

Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!