A Labradorite feldspar from the plagioclase group with 68% albite and 32% anorthite. Copper gives color that is sometimes a clear red or green, sometimes dichroic (red and green) in the center of the stone. Copper sometimes forms quantities of small reflective plates that lie in bands (lamellar twinning). The Indian and Norwegian "sunstones" used for cabochon cutting are often classified as oligoclase but sometimes as labradorite. Inclusions are not copper but hematite or goethite.

Physical properties:

Optical properties:

Facet angles (pavilion/crown):

Cutting lap:

Medium or fine grit

Facet polishing:

Cabochon polishing:

Orienting:

Yellow stone without orientation pattern. With moderate schiller, banding parallel to the table facet. With strong schiller, orient the banding perpendicular to the table facet to achieve a red stone or to cut a cabochon. Stones with red or green color centers should be oriented with the most color in the crown. Often, even the table facet does not need to be oriented away from the plane of the cleavage plane.

Treatments/synthetics:

None known

Tips!

Sometimes it can be difficult to polish - try using a LightningLap CeOx for better results.

Here is a link to a great page on how to orient Oregon Sunstone. http://doubleeaglemine.com/Cuttingtips.html

Oregon Sunstone rough

Sunstone on Gemdat