Types/Color:

• Bytownite – Pale yellow to brown.

• Labradorite – Pale yellow to gray with play of color.

• Orthoclase – Colorless, champagne to yellow.

• Sunstone – Colorless, champagne, copper inclusions can produce a red or green color.

Moh’s hardness: 6-6.5

Refractive index: 1.52-1.568

Critical angle: 41°

Specific gravity: 2.5-2.7

Cleavage: Perfect in 3 directions.

Fracture: Uneven, somewhat brittle.

Bytownite Faceted Gemstones

Dispersion: Low (.012), but the combination of a high polish and minute inclusions can simulate the effect of moderate dispersion.

Heat sensitivity: Low

Pleochroism: None

Birefringence (double refraction): Weak to medium (.005-.01)

Crystal structure: Triclinic (bytownite, labradorite and sunstone) Monoclinic (orthoclase).

Cutting: Cleavage usually doesn’t present a problem. Sharp corners have the tendency to chip out when cutting.

Polishing: Cerium oxide on most common laps.

Comments: If cutting an Oregon sunstone with a pocket of color, put the colored area at the culet of the stone.  This will impart the color to the rest of the stone.  If there is strong shiller, then it will be better to cut the stone as a cabochon.