Sunstone

It’s not often that one has the opportunity to write about a gem that’s found solely in the United States. But the occurrence of transparent feldspar along with native copper mineral deposits occurs only in Oregon. Feldspar crystals are fairly common in volcanic basalts all over the globe, but their quality is rarely high enough to be used in jewelry. What makes Oregonian sunstone even more rare is that Oregon is the only place where copper is found along with volcanic flows. When this copper is introduced into the feldspar crystals as tiny platelet inclusions, the result is Oregon sunstone.

History and romance. Sunstone is mined in the “Oregon outback” in only two places, about 100 miles apart. The Ponderosa mine is located in the northern part of southeastern Oregon’s Harney County. The Dust Devil mine is near Plush, centrally located in Oregon’s south- central Lake County. Both deposits are exposed to gem hunters, who can find the gems scattered on the ground. But start digging, and you’ll find stones worth all the effort you expend to acquire them.

Historical references claim that the gem has been “mined” by Native Americans for a few centuries. Actually, they were just picked up off the ground. Small-scale digging operations have been mounted only within the past century, and in earnest even more recently, since the 1990s.

If you’re not familiar with sunstone, you’re not alone: Most people ignore the feldspars. Maybe that’s because the gem feldspars are typically ornamental translucent to opaque materials. Or maybe they’re ignored because the mineralogical classifications, linked with their common varietal names, are just simply too complicated or confusing for most people to understand which stones are actually from the feldspar group. For example, moonstone and labradorite are the two most commonly known feldspars. Moonstone is both an oligoclase and orthoclase feldspar. Oligoclase and labradorite are both plagioclase (calcium) feldspars. Orthoclase is a potassium feldspar. Another recognizable feldspar is the gem amazonite, which is a microcline (also potassium) feldspar.

Sunstone is both a labradorite and oligoclase feldspar. Some sunstone has hematite inclusions to give it its aventurescence. The sunstone from Oregon is believed to be the only material to have copper platelets that cause the aventurescent sparkle, also called schiller. All of these classifications and descriptions can be confusing, especially since most labradorite feldspar is known mainly for its use in office building walls or kitchen counters—not jewelry.

Qualities and value. Much to the dismay of some mineralogists, all of the material from Oregon—whether or not it contains copper inclusions—is called sunstone. Transparency and depth of color is critical for sunstone that is without the schiller-causing inclusions. But if it’s sparkle you want (and that is, after all, the reason for the gem’s name), then it should either form some interesting pattern or, better yet, be homogeneous throughout. Some prefer to have the schiller effect oriented to show up only as the stone is tilted back and forth. Others prefer to have the copper platelets arranged so that you see a blanket of schiller across the face of the stone when looking at it straight on. One common preference is to have the schiller centrally located, as opposed to occurring off to one side. Strength of color and aventurescence are the key elements to the value of an Oregon sunstone.

Color variations. Oregon sunstone comes in a variety of colors ranging from nearly colorless to a pale green, orange, or red. Ponderosa sunstone can be found in incredibly saturated reds, with lots of copper schiller. Dust Devil sunstones appear more in peach and green colors, with less schiller, and in a wider range of colors than Ponderosa material. Both localities produce gems with strong pleochroism. This means that, depending on the orientation of the gem, you will see one color or another. In addition, there are zones of color that can be seen in one direction. All of these factors must be considered before fashioning the gem. What makes it even more complicated for the cutter is that the rough typically has a colorless or near-colorless outer skin, an inner layer of green, and then finally a central red core.

Enhancement. Sunstone is cut and polished—that’s all. There is no heating, irradiation, oiling, or waxing of sunstone, making it one more stone to add to the short list of gems that are not enhanced.

Pricing. According to The Guide, the cost of fine-quality sunstone can range somewhere between $150 and $300 per carat for stones in the one- to three-carat range. Extra-fine-quality in all sizes can reach up to $1,000 per carat. The pale-colored yellow gems are considered to be of lesser quality, while the deep greens, reds, and bicolors are labeled extra-fine. Cabochon material can be priced at approximately 75% of the faceted material. Much of the material is now being carved by gem artists, and this material must be priced based not only on the quality of the material but also on the quality of the carving.

Care and cleaning. Sunstone is fairly durable, although at 6.5-7 on the Mohs hardness scale, it’s softer than many gems and should be handled carefully. Ultrasonic cleaning is fine, as long as the gem is protected from contact with other gems or jewelry. It’s probably better, however, if you can use a gentler cleaning process.

Recommended reading. For more information, see the following reference:

Lapidary Journal, “Dust Devil’s Sunstones,” January, 1998.

Acknowledgements
Special thanks to Marty Guptill of Foolish Hearts Gems (creators of custom-faceted gemstones) and all the nice folks at Dust Devil Mining Company.