Spectrolite Gem Cutting Advice

Question: I recently purchased a chunk of Wyoming spectrolite (or labradorite). I would appreciate any orienting tips for slabbing, cutting, and polishing.

Answer: Gem orientation is critical for cutting spectrolites and other labradorites with color flashes. However, not every labradorite that shows color flashes is a spectrolite.

What is a Spectrolite?

Although you'll see the names spectrolite and labradorite used interchangeably, this isn't correct. Spectrolite is a trade name of labradorite feldspar from Finland that displays an unusual range of labradorescence, a flash of metallic color on the surface of the stone. Spectrolite shows strong flashes of multiple colors.

Other varieties of labradorite from sources around the world may also show flashes of multiple colors. Although vendors sometimes call these stones "spectrolites," reserve that name for those pieces from Finland.

Orienting Spectrolites and Other Color-Flashing Labradorites

The most important thing when cutting labradorite is the orientation. Get your rough wet and turn it until you get a good flash of color. Mark this as the "top." (I've bought irregularly shaped labradorite and could still get a good clear starting mark).

Next, saw the rock in layers so that this color will be flat across each slab cut. If you get more than one flash, choose the strongest. I doubt any grinding will be needed to see this color. If you don't orient your rough, you'll wind up with a translucent gray stone without any desirable color flash.

E. Jakeman

Ogden, Utah