Rapaport Magazine
Colored Gemstone

Potch Appeal

Everyone loves precious opal, but its cousins, opaque pink or blue opal, garner admiration as well.

By Sheryl Jones

John Apel
Opaque hues of blue Caribbean waters and petal pinks have made Peruvian opal a popular choice with designers. Considered the national stone of Peru, these opals are found in the country’s Andes Mountains. According to folklore, the ancient Incas considered opals as a gift from Pachamama, their goddess of fertility.
   So different in appearance from a precious opal, the Peruvian opal might not even seem to be an opal at first glance. Known as a potch or common opal, these stones lack the “play of color” — the flashes of fire orange, intense red, jet black and white — that characterizes precious opals according to the Gemological Institute of America (GIA).

What are Peruvian Opals?
   Like all opals, Peruvian opals consist of hydrated silica. The silica spheres bond together with water and additional silica, forming the stone in the seams of the mine where horizontal or vertical deposits of the material are sandwiched between other sedimentary rock. The opal is amorphous, meaning it has no crystalline structure or chemical composition and is therefore considered a mineraloid rather than a mineral.
   The Peruvian blue opal gets its color from submicroscopic inclusions of a copper mineral called chrysocolla. Depending upon the levels of copper, it can be as spectacular as the Paraiba tourmaline gemstones that sell for $1,500 per carat, compared to the $150 per carat price of the finest Peruvian blue opal. “The highest-quality color hits all the senses. It is like holding a tropical vacation in your hands,” says Helen Shull, co-owner of Out of Our Mines in Dyer, Nevada.
   The Peruvian pink opal gets its color from a clay mineral known as palygorskite. The presence of larger amounts of this material intensifies the color. Sometimes this pink opal gets mistaken for pink chalcedony, but the angel skin and rare reddish colors of the pink opal are distinctive.
Precious opal is considered a soft stone and sometimes unstable due to its high water content. But pink opal has a higher silica content than other material, including the blue variety, making it more stable and harder at a 6.5 on the Moh’s scale of hardness compared to 5.5 for blue.
   While generally called Peruvian opals, the pink and blue opals are also mined in the U.S., Australia and other countries.

From Mine to Market
   Debuting at the 1998 American Gem Trade Association (AGTA) show in Tucson, Peruvian blue opal was an instant draw, attracting buyer interest with its variety of colors, from brilliant blue to mint green. Its pink-hued sister became equally sought after as one of the few pink gemstones that range from pale opaque pink to a very rare reddish pink tone.
   The Peruvian opal’s journey to Tucson began in 1983, with the local miners, who were working leased copper mines in the Andes in southwestern Peru. Blue opal is mined in the Arequipa region and pink opal is mined in the Ica district, which is north of Arequipa.
   Miners brought the goods to Lima because they wanted to keep the mines’ location secret. They sold rough to dealers from Germany, who bought the premium quality goods, and to dealers from India, who purchased the lower qualities.
   According to Lee Horowitz, co-owner of Peru Blue Opal Ltd., a miner and manufacturer, and a noted world authority on Peruvian opals, “Back in the late 1990s when Peruvian opals hit the height of popularity, the mines were yielding as much as 50 kilos to 100 kilos in every four-to-eight week period, with a first run of superior quality, which is an even color that is translucent to opaque. In that same time frame, the mines yielded about 30 kilos to 40 kilos of premium blue material, which is considered the highest-quality translucent material.” As demand for the stone grew, miners started using jackhammers to cut larger pieces of material in order to make large beads in sizes of 30 mm. However, as they cut wider, the amount of premium and superior blue material dwindled.
   The pink opal shared a similar fate. “At first, in the Ica district, during the late 1990s, huge amounts — 100 kilos — of superior pink opal were mined in every four-to-eight week run. Then it started to run out and limited amounts, around 5 kilos to 25 kilos of superior quality, were mined,” says Horowitz.
   In 2010, copper prices skyrocketed and miners turned their attention to copper ore because it was much more profitable than mining opal. These small miners became millionaires overnight from copper and stockpiled the pink opals and blue opals to keep demand high.
   The strategy worked. Since then, Peruvian opal has remained popular, with steady demand for the best material. The top qualities, premium and superior, are now very hard to find. Horowitz says high-end premium, which he describes as “super Windex-color blue, with no matrix — the dark veins running through the stone — even color saturation and translucent” has almost disappeared. Most material is cut into cabochons, but some pieces of this quality of material are so clean and translucent that they can be faceted.

Quality Factors
   The best qualities for pink opal are categorized into top premium, which is an extremely rare reddish color due to an overabundance of palygorskite, and then first quality, which is characterized as Angel skin, which is an even color and can also be semitranslucent.
   Even though there is high demand for the best quality pink opals and blue opals, there is also a large market for the lesser-quality material, a good portion of which is manufactured into beads. Horowitz says miners have broken down the lower-grade material into several categories for blue material. First quality has even to some uneven color ranging from medium to lighter blue, blue greens and greens and may have a matrix. Then there is second/third quality, which is uneven, washed-out blues and greens, with matrix. The last category is mine run, which is basically white opal and is usually dyed overseas in India and China.
   The lesser-quality pink material is categorized into second and third qualities, which usually exhibit uneven color. However, since the pink opal is harder than the blue opal, it can produce a high polish and is made into beads.
   “When staring into the fluid, pearly nature of a Peruvian opal, it looks like it is shifting and changing like the future of infinite possibilities,” concludes Annie Law, owner of Anari Jewelry in New York.

Article from the Rapaport Magazine - July 2015. To subscribe click here.

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