Twenty years ago at a flea market on Long Island, Stuart Wilensky bought a $50 quartz crystal from Arkansas that transformed his life. Wilensky was finishing a master’s degree in Byzantine art, but the crystal whetted his appetite for another kind of visual treasure: sculptures forged by the earth itself. Today Wilensky, based in Middletown, N.Y., is a top collector and dealer in the field of fine minerals. And his collection has evolved light-years beyond that $50 quartz. Its crown jewel is Excalibur, a pair of tourmaline crystals, ranging in color from pink to green, that plunge as one into a white quartz base, or matrix. Excavated from Brazil and appraised in the million-dollar range, the piece resembles King Arthur’s legendary sword in the stone.

Excalibur, from Minas Gerais, Brazil, is a tourmaline on matrix
 
With his background in art history, Wilensky is well prepared to serve clients who entered the mineral market in the 1990s, many of whom were also art collectors. Thanks to the stock market boom, it was also a period when prices paid for rarities skyrocketed. What happened, says Joel Bartsch, curator of the gem and mineral collection at the Houston Museum of Natural Science, is that minerals—geological accidents that have miraculously survived the excavation process—came to be viewed as works of art. Where once collectors had chosen specimens based on scientific merit, they now began to select according to aesthetics.
 
Hoarding rocks and gems is not a new activity. High-end mineral collecting has been the sport of kings since the 16th century, Bartsch says. Its practitioners included both Peter the Great and Catherine the Great. By the end of the 19th century, however, robber barons replaced royalty at the top of the collecting heap. With guidance from George Kunz, a self-taught gemologist who ran the gem and mineral department at Tiffany, such true-blue American capitalists as J.P. Morgan and Andrew Carnegie amassed formidable troves, which became the cornerstones of collections at the American Museum of Natural History in New York and the Carnegie Museum of Natural History in Pittsburgh, respectively. Many believe that the greatest American collection was assembled by Washington Augustus Roebling, chief engineer on the Brooklyn Bridge. Roebling supervised the underwater placement of the massive caissons that support the bridge, but the effects of rapid decompression on a diver’s body were not understood in the late 19th century. As a consequence, Roebling developed a chronic case of the bends, and embraced mineral collecting during his convalescence. His 16,000 specimens of rocks and minerals, donated to the Smithsonian Institution after his death in 1926, form the core of its mineral and gem collection.

Wilensky's 5-inch silver wire comes from Kongsberg, Norway, which is known for its silver mining districts that produce sculptural silver wire.
 
Collectors place mineral specimens in four categories: “thumbnails,” which mea-sure around one square inch; “miniatures,” up to two square inches; “cabinet specimens,” ranging from two to five square inches, and “museum-size specimens,” which are greater than four square inches. Although minerals as wide as four feet have been found, they are impractical to store and are generally broken up for sale.
 
Collectors seek the same qualities in minerals as they would in art—vivid color and a pleasing sculptural arrangement. “Provenance also comes into play here,” observes Irv Brown, proprietor of Irv Brown Fine Minerals in Fallbrook, Calif. One of the treasures in his personal collection is a piece of kunzite (named for George Kunz) that belonged to Andrew Carnegie.
 
“A good mineral specimen of a gem crystal can go for 10 times more than its cut value,” Brown adds. Silver, for example, trades at $4 an ounce, but a particularly exquisite specimen of wire silver—the mineral, in nature, looks like “a serpent about to strike,” Brown says—can command hundreds of thousands of dollars. “Perfection is absolutely the key,” says Bartsch. Clean repair is very acceptable, but minor breaks to tiny crystals can shatter the value of a piece. What isn’t acceptable, however, is fraud—affixing a crystal to a matrix to which it was not attached in nature.

Wilensky's Nigerian tourmaline ranges from green to pink.
 
Price is also affected by a mineral’s origins. Proustite from Germany, for example, is rarer than proustite from Chile and, consequently, more valuable. In recent years, the finest specimens have been unearthed in countries such as China, Brazil, Pakistan and India, where labor is plentiful and minerals can be excavated by hand. In the United States, crystals have emerged from mines dug for other substances, such as gold or silver. But mechanized U.S. mining techniques, structured to yield the greatest quantity of ore per hour, frequently destroy rarities in the process.
 
Cutting-edge technology can, however, transform an exhausted gold or silver mine into a rich source of crystals. In 1991, with a group of backers, Bryan Lees, a geological engineer and the president of The Collector’s Edge in Colorado, reopened a 19th-century mine to prospect for crystals. Through the use of diamond chain saws and other state-of-the-art extracting techniques, the mine has yielded pristine specimens of rhodochrosite, some worth over $100,000.
 
The Internet is awash with web sites devoted to rocks and gems, but the value of specimens is sometimes inflated online, so many reputable dealers recommend that beginners buy at trade shows. “If a dealer says, ‘This is the best in the world’ about a specimen, make sure it’s not just hype,” cautions Wayne Leicht, a former aerospace engineer who more than 30 years ago cofounded Kristalle, a fine mineral business in Laguna Beach, Calif.

Wilensky's transparent tanzanite, found only in Tanzania, dazzles in blue, purple and red.
 
Leicht encourages collectors to learn as much as they can by visiting museums, studying periodicals and attending trade shows. The three top mineral magazines are Mineralogical Record, published in Tucson, Ariz.; Rocks & Minerals, published in Washington, D.C.; and Lapis, a lavish German-language photojournal published in Munich. Leicht also recommends building a library, beginning with such basic reference books as Peterson’s Field Guide to Rocks and Minerals by Frederick Pough. Collectors will want to study stones at the Smithsonian, the American Museum of Natural History and the Natural History Museum of Los Angeles County. But they shouldn’t spurn smaller collections. Houston’s Museum of Natural Science, for instance, has a mere 4,000 specimens, but many are important, including one Bartsch refers to as the “Mona Lisa of the mineral world.” Nicknamed the Rabbit Ears Tourmaline, it features two crystals on a quartz base that bring to mind the Playboy bunny.
 
Nearly every weekend, some U.S. city hosts a mineral trade show. The biggest and best known takes place in mid-February in Tucson, Ariz. Some collectors, however, deliberately avoid these spectacles. “I know myself,” confesses Peter Via, a crystal collector from Roanoke, Va. “I’m an impulse buyer. If I went, I’d come back with my entire net worth in the back of an 18-wheeler.”
 
Although most minerals change hands through dealers, they have also been sold at auction, with mixed results. In January 2001, when the mineral collection of Joseph A. Freilich was auctioned at Sotheby’s in New York, many lots remained unsold. “It was a confusing affair for many collectors,” Wilensky recalls. Most had never bought at auction before and didn’t like the split-second bidding. By contrast, Freilich’s library of antiquarian mineral books, items more familiar to Sotheby’s regular buyers, sold for over $10 million, higher than its estimate.
 
Many mineral collectors have a personal relationship with their dealers, says Wilensky, who bought much of the unsold material from Freilich after the auction. And dealers do their best to preserve those relationships. “I’m an incurable collector,” Wilensky admits. But he limits his collection to 100 specimens. That way, he says, “my customers don’t think I’m keeping everything that’s good.”
 
Stuart & Donna Wilensky's aquamarine and 140 carat faceted stone from India