It is generally thought that quartz, the rock family that gives jewelers such gem staples as amethyst and black onyx, is the most common mineral on earth. Think again, some geologists say. That distinction rightfully belongs to feldspar, a rock group whose most famous gem member is moonstone.
But whether or not feldspar is the most common mineral found on earth, it just might be the most common mineral found around the home—at least in America. Feldspar, both in ground-up rock and clay form, is used in numerous home and beauty products. If, for example, you’ve got five bricks in the den or Soft Scrub cleaning products in the kitchen, then you’ve got feldspar on the premises.
Miner Chris Johnston would like to see Oregon sunstone added to the long list of household feldspars. And with savvy gem marketers ranging from Tiffany’s to the QVC home shopping network already promoting sunstone, Oregon’s state gem could be poised for its widest acceptance ever. Indeed, it might even unseat moonstone as the world’s ranking feldspar.
Two factors are working in the American gem’s favor to boost demand: quality and quantity. At their best, Oregon sunstones boast the traditional red and orange colors associated with this gem, as well as a wide variety of unique greens never before seen. Occasionally, pieces of rough are free enough of inclusions to permit faceting. Sunstones from India, the other major source of this gem, are invariably cut in cabochon form. Furthermore, Oregon’s present production dwarfs any from before it both here and abroad. As a result, principals of the state’s seven feldspar mining operations bank on growing jeweler interest in sunstone.
From Out of Nowhere
In 1991, gem feldspar became the fourth most important gem in terms of dollar value mined in the United States- up three times to $1.5 million from $500,000 in 1990. Of this production, most by far was sunstone from the Ponderosa Mine in eastern Oregon’s Ochoco National Forest. Discovered in 1980, the mine accounted for two-thirds of all America’s feldspar output just three years after it was taken over by Chris Johnston and Larry Gray in 1987.
When U.S. feldspar production leaped 40% ahead in value of tourmaline ($500,000 versus $350,000), America’s most famous gem, in 1990, even miners were stunned. Was sunstone becoming all that popular? “We wouldn’t have doubled production every year since 1989 if there wasn’t demand for the gem,” Johnston, based at One Track Mines. Boise, Idaho, answers.
Now with feldspar production for 1991 nearly 135% greater in value than that of tourmaline, sunstone seems set to overtake Arizona peridot, America’s third-ranked gem in terms of economic importance. In 1991, says the U.S. Bureau of Mines, production of this olivene was $1.75 million vs. $1.49 million for feldspar, the lion’s share of it from the Ponderosa Mine. “We are now producing 12,000 to 17,000 carats each operating day,” says Johnston. “I know of only one mine with greater output per operating day: the Eldorado Bar Sapphire Mine near Helena, Mont., which is currently producing as much as 50,000 carats a day.’
Oregon feldspar is known by two names, “sunstone” and “helioite” (the latter a recent coinage based on the Greek word for sun, helios). Of the two names, “sunstone” is usually preferred by those familiar with both. How sunstone got its name is not known. Some think it originally referred to the gem’s similarity to the color of the setting sun. Others think the name stemmed from its reddish glints reminiscent of metal-flake paint.
Most likely it’s the latter, for sunstone is usually thought of as a phenomenon stone, thanks to the millions of copper platelets or hematite particles found in the Oregon and Indian varieties respectively. The spangled light reflections caused by these inclusions are variously and interchangeably described with play-of-color terms such as schiller (a German word, often used with moonstone, for a bluish or white sheen), “labradorescence” (vivid colorations in certain feldspar family members) and “iridescence” (intermingling of brilliant colors).
Curiously, none of these terms is correct for Oregon sunstone, according to Johnston. Since the special effect for which this gem is known has more to do with light than color, the most accurate term, Johnston says, is the one least used: “aventurescence” (derived from the Italian word aventure, which means “by chance”). This is ironic since sunstone is classified by mineralogists as aventurine feldspar. The word “aventurine,” like “aventurescence,” refers to the spangle phenomenon.
Welcome to the Big Time
With a hardness of 6 to 6½, sunstone is roughly equivalent to tanzanite, making it theoretically more suited for earrings and pendants than rings. But since at least 75% of all tanzanites end up in rings, and we have yet to hear of widespread problems arising from this fact, we assume most Oregon sunstones will also be worn on fingers. Customer buying them for or in rings should be told not to take these stones for granted.
Unlike tanzanite, most jewelry sunstones are cabochons. Of the 1 million carats of rough sunstone taken from the Ponderosa Mine in 1991, 95% was cabochon grade. After cutting 50% in America, 50% in Asia, these cabs sold for between $2 and $200 per carat, the bulk of them in the $25 to $50 per-carat range.
Realizing most readers are still as unfamiliar with Oregon sunstone as we were, we inspected thousands of carats of goods for this article. Most were various shades of red and orange—from plum and raspberry to peach and salmon—while Indian stones tend to have golden or yellow body colors.
Where Oregon sunstones are beyond compare with others. Ponderosa Mine in the realm of faceted goods. Last year, the sunstone is produced 50,000 carats of facetable rough (5% of the mine’s output). This rough yielded around 7,500 carats of cut stones, most red and orange but many unique forest- and blue-greens. Of this group, 75% were under 1 carat and sold to jewelers for $75 to $150 per carat in fine qualities; 20% were between 1 and 3 carats and fetched $300 to $500 per carat in top grades. The best of the handful stones between 3 and 10 carats commanded $1,000-plus per carat. Of these, a magnificent 5.04-carat ingot-red stone sold for $1,500 per carat, proof that Oregon sunstone has made it to the big time and big money.
Please note: this profile was originally published in 1992 in Modern Jeweler’s ‘Gem Profiles/2: The Second 60’, written by David Federman with photographs by Tino Hammid.
The sunstone in the header image weighs 1.65 carats and is courtesy of the Ponderosa Mine, Boise, Idaho.