A Is For Alexandrite...

The unofficial glossary of exotic gems

I love it when someone has to ask, 'What's that stone?' " says designer Nicholas Varney, who is especially excited to hear the query regarding earrings he's just finished crafting from a stockpile of Sri Lankan chrysoberyls. Varney isn't the only jeweler educating curious clients about rare and lesser-known gems. This was the year Mish Tworkowski fell for "intoxicating, enveloping" blue zircon, John Hardy for cat's-eye tourmaline that "comes alive in sunlight," Laura Munder for "delicious-looking" mandarin garnet.

The laws of supply and demand rendered the line dividing the precious—diamond, sapphire, ruby, emerald—from semiprecious stones obsolete about a decade ago. (This made perfect sense to those in the know, since many of the stones labeled less precious were becoming equally as rare.) The change allowed designers to expand their palette and shoppers their jewelry vocabulary.

Using these specimens—with unfamiliar names like sugilite, tanzanite, and Paraíba tourmaline—also allows jewelers to show off a little. "It indicates you have a certain knowledge and expertise in the gem world," says designer and gemologist Tito Pedrini. "Everyone knows the classics. These stones set you apart." For jewelry lovers the appeal may be more about the intense red of a spinel or the delicate green of a beryl, but they are also lured in by the stories surrounding exotic jewels. "Clients want to hear about the mythology and about the stones' ancient healing or magical powers," designer Irene Neuwirth says.

Before the busiest jewelry shopping days of the year, a crash course in exotic gems and stones unfamiliar.

ALEXANDRITE
FAMILY: Chrysoberyl
Like a seventies mood ring, alexandrite changes color in different light, appearing green by day and raspberry red by candlelight. SOURCE First discovered in 1830 in Russia's Ural Mountains on Czar Alexander II's coming-of-age birthday (hence its royal name). SUPPLY Almost gone. The most important specimens are found primarily in period pieces, such as Cellini's 16-carat alexandrite, purchased from a Palm Beach socialite's estate. SEE Cellini ring, price upon request; 212-751-9824.

BLUE ZIRCON
FAMILY: Zircon
A naturally occurring electric-blue gem that isn't to be confused with the fabricated cubic zirconia. SOURCE This gemstone popped up in a Cambodian mine four years ago. SUPPLY That mine is now close to drying up. SEE Mish's multistrand necklace, $28,000; 212-734-3500. Also, Alex Sepkus's blue zircon in a finely detailed gold ring, $4,725; 212-391-8466.

CAT'S-EYE PINK TOURMALINE
FAMILY: Tourmaline
Technically known as chatoyant, cat's-eye gets its nickname from the vertical band of light that appears to open and close as the stone is turned (the result of light hitting natural silky fibrous inclusions). SOURCE Today Brazil, Tanzania, and Sri Lanka are the main places to find cat's-eyes. SUPPLY While the stone is abundant in green, designer John Hardy has spotted only six pink cat's-eye tourmalines in his entire career. SEE Hardy's bracelet, $25,000; 866-542-4682.

CHRYSOBERYL
FAMILY: Chrysoberyl
The often overlooked stepsister of alexandrite, chrysoberyl has been deemed the gemstone of springtime, youth, and innocence because of its golden-honey hue. Its color also leads some to confuse it for peridot. SOURCE Sri Lanka and Brazil are the primary sources. SUPPLY Despite having a reputation as low man on the gem totem pole, large high-quality chrysoberyls are quite difficult to come by. SEE Nicholas Varney's chrysoberyl, moonstone, and diamond earrings, $68,000; 561-655-5850. Also, Smithwick Dillon's necklace with chrysoberyl clasp, $9,000; 305-531-8383.

CHRYSOPRASE
FAMILY: Chalcedony
This green stone is cited in 11th-century Byzantine manuscripts as a remedy for weak eyes. SOURCE Sometimes called Australian jade; deposits have been found in Marlborough and Queensland. SUPPLY Scarce. The only stock left is in Australia. SEE McTeigue & McClelland bracelet, $7,800; 800-956-2826.

GREEN BERYL
FAMILY: Beryl
When beryl occurs in pure green form, it is labeled an emerald; if nature colors it blue, it's an aquamarine. But at times it falls somewhere in between, and then it's called green beryl. SOURCE Brazil, Madagascar, Afghanistan. SUPPLY In high demand. It recently shed its reputation as the poor relation of its precious siblings, becoming something of a designer's darling. SEE Kwiat's earrings, $50,000; 800-927-4367.

IMPERIAL TOPAZ
FAMILY: Topaz A peachy-pink bijou currently found exclusively in a single Brazilian mine. SOURCE First sourced in Russia when ownership was restricted to the czar, hence the regal descriptor. SUPPLY Most of what's left is owned by the Brazilian jeweler H. Stern. The company has been hoarding imperial topaz for the last 60 years. SEE H. Stern's pendant necklace, $93,000; 800-747-8376.

IOLITE
FAMILY: Cordierite
From the Greek word ios, meaning violet, the stone was a favored trinket of the Vikings'. SOURCE Leif Eriksson probably found his in Norway or Greenland; today iolite is mined in India, Sri Lanka, and Mozambique. SUPPLY Available but going fast. SEE Nancey Chapman's rough-cut necklace, $8,200; 888-523-7787.

KUNZITE
FAMILY: Spodumene
A decidedly feminine bauble appearing in shades from pale pink to lilac. SOURCE The first significant deposit of the stone was unearthed in 1902, in the Pala region of California. Its name comes courtesy of George Kunz, the legendary gem buyer for Tiffany & Co. SUPPLY Dwindling due to increased demand. SEE Verdura's "wrapped" heart brooch, $57,500; 212-758-3388. Also, Tiffany & Co.'s multistone kunzite necklace, $235,000; 800-526-0649.

LABRADORITE
FAMILY: Feldspar
It looks as though it could be a black moonstone—if in fact there were such a thing. The gem gives off a mélange of gray-blue colors with tinges of red, orange, and green. During ancient times labradorite was hailed as a cure for headaches and stress. SOURCE The Canadian island of Labrador housed the original stockpile, way back in 1770. SUPPLY Currently available from mines in Madagascar. SEE Irene Neuwirth's necklace, $8,100; 212-206-1272.

MANDARIN GARNET
FAMILY: Garnet
The orange gem conjures up images of a spectacular African sunset for some. To others, like designer Laura Munder, who uses it in a bold brooch, it resembles a jelly bean. SOURCE Mandarin garnet was discovered in 1991 near the isolated Kunene River between Namibia and Angola. SUPPLY Dwindling. The Kunene River mine dried up and a deposit in Nigeria is a few years away from also being mined out. SEE Tamara Comolli's bracelet, $23,000; 239-434-2800. Also, Francesca Visconti's multistrand necklace, $6,000; 212-593-6106.

MEXICAN FIRE OPAL
FAMILY: Opal This fiery stone exudes a brilliance that the Aztecs believed gave wearers courage. Other tribes saw fire opals as a symbol of the deepest love. Modern-day designers such as Sharon Khazzam like it because the gem seems "alive inside." SOURCE Not surprisingly, the most important of these stones are found in Mexico. SUPPLY Its bold color is now in vogue, which means mines are starting to run dry. SEE Khazzam's fire opal-studded gold cuff, $17,800; 888-822-7639.

PARAIBA
FAMILY: Tourmaline
This bluish-green gem is so unusual that a Brazilian miner first presented it to Hans Stern of H. Stern as clear turquoise. Immediately intrigued, Stern had the stone tested and discovered that it was, in fact, the more precious tourmaline. SOURCE After almost an entire decade of digging through the mines in Paraíba, Brazil, Heitor Dimas Barbarosa hit pay dirt in 1967. SUPPLY Extremely limited. Paraíbas are at the top of gem collectors' Most Wanted list. SEE Mimi So's necklace, $75,000; 212-354-1407. Also, H. Stern's four-carat ring, $220,000; 212-688-0300.

PERUVIAN OPAL
FAMILY: Opal This pretty opaque rock is, in the words of British designer Stephen Webster, "so fresh-looking, even jewelers sometimes don't know what the hell it is." SOURCE Webster got his from a Peruvian miner at the annual Tucson gem show. That miner's most likely source was the multiple deposits near the Andes. SUPPLY Not as rare as the black opal but still limited. SEE Laura Munder's earrings, $29,700; 877-686-3372. Also, Webster's opal and gold necklace, $16,870; 310-550-5900.

RUBELLITE
FAMILY: Tourmaline
This pinkish-red gem is sometimes taken for a ruby or a spinel. SOURCE Mines in Madagascar, Afghanistan, and Pakistan are well stocked. SUPPLY Of all the pretty red stones, rubellites are the most abundant. "I can get a twenty- or forty-carat rubellite. You just can't locate spinels or rubies that big," says designer James de Givenchy. SEE Favero's necklace, $11,400; 877-714-2200. Also, Samuel Getz's rubellite ring, $10,500; 305-448-4567.

SPHALERITE
FAMILY: Sphalerite
From the Greek word for deceit, this obscure stone can stump even the most die-hard gem enthusiast. The incredible brilliance makes it look almost fake. But sphalerites are for real: All that radiance comes from the fact that they have a higher refractive index than diamonds. SOURCE There's a recorded discovery in Franklin, New Jersey, but the two most important mines are in Mexico and on Spain's northern coast. SUPPLY Scarce. SEE Eclat's 35-carat pendant necklace, $28,000; 212-581-2446.

SPINEL
FAMILY: Spinel
Sometimes called the great imposter, as it can easily be mistaken for a ruby. In fact, Queen Elizabeth's famed Timur Ruby was later revealed to be a 352-carat red spinel. SUPPLY Erratic. Spinels are smuggled out of Burma by gem traffickers who risk their lives transporting the stones from the volatile country into Thailand. SEE Elizabeth Locke's gold bands, from $2,700; 212-744-7878. Also, Harry Winston's cushion-cut four-carat ring, $40,000; 800-988-4110.

SUGILITE
FAMILY: Sugilite
A purple rock available in large sizes. SOURCE First found in southwestern Japan in 1944 by petrologist Ken-ichi Sugi. Now it's mostly in southern Africa. SUPPLY Limited. SEE Vhernier's dome ring, $4,800; 212-753-4000.

TANZANITE
FAMILY: Zoisite
Appears in a range of blues reminiscent of sapphire. SOURCE Tanzanian miners discovered the stone in 1967. When they brought it to Henry Platt, great-grandson of Louis Comfort Tiffany, he decided that blue zoisite (its technical name) sounded too down-market. They renamed it tanzanite and introduced it to the jewelry world two years later. SUPPLY Limited. SEE Tiffany & Co.'s tanzanite brooch, $400,000; 800-526-0649.

TSAVORITE
FAMILY: Garnet
Some call this deep-colored stone a green diamond. SOURCE Tsavorite was initially unearthed in Kenya's Tsavo National Park in 1968. Today it's highly sought after in Tanzania and Kenya. SUPPLY Scant. Gemstones that are larger than two carats are almost unheard of. SEE Antonini ring, $2,840; 212-223-9333.