In the Old World, Egyptians, Greeks, and Romans cherished these bewitching green stones. Potentates of India and Persia clamored for them. In the New World, Spaniards seized Colombian emeralds such as these adorning a gold cross from the Atocha, a Spanish galleon that sank off Florida in 1622, The cross and its gold chain recently sold for $1.3 million.

Emerald, far and away the most prized and expensive of the beryls (minerals composed of beryllium aluminum silicate) have been known since at least 3500 B.C. The earliest sources of emeralds, the legendary Cleopatra’s Mines, are located in the Sikait-Zabara region of Egypt near the Red Sea. Egyptians worked them for thousands of years, followed by Alexander the Great, Romans, and Turks.

One of 12 stone in the breastplate of judgment described in Exodus was called an emerald, and, if real, no doubt came from Cleopatra’s Mines. According to Revelation, the fourth foundation of New Jerusalem’s walls, where the pearly gates were located, was garnished with emeralds. But were they the real thing? Many early references to emeralds in biblical and Roman times pertained to peridot, a green gem found at the time on St. John’s island (Zabargad) in the Red Sea.

With diamonds the best color is the absence of color. The abiding allure of emeralds lies in their unique color. Pliny the Elder, a Roman scholar, wrote. "No other color is more

In the mid-19^th century, mineralogists decided that an emerald was any beryl colored by chromium (less than one percent) and green enough to be valuable. This definition, strict on chemistry but loose on color, served for a century, until a 1963 Brazilian find at Salininha of rich green beryls colored by vanadium.

But how green must a beryl be before it is called an emerald? Even the GIA has trouble with this one because stone colors span a spectrum from pale yellow-green to lush bluish green, depending on their chemistry. Richard Liddicoat, the GIA’s chairman, say, "Every-one except some Europeans have agreed on the chromium –vanadium issue. We say if a beryl has emerald color, it’s an emerald." That works almost all the time-but not with green beryl, a variety colored by iron. "Green beryls," says Liddicoat, "should really nor be called emeralds, even though they’re deep enough green to be emeralds."

Other beryls are goshenite, a colorless stone; pale green beryl, which is often heated to produce aquamarine; aquamarine itself golden beryl, which is being marketed as American Red Emerald.

The world of emeralds changed forever when the Spanish arrived in South America in the early 1500s. Although they originally plundered gold and silver, the conquistadors had also seen emeralds in Mexico and went looking for their source. By the time they fought their way through Colombia’s mountains to the area around Chivor in 1537, they had looted more than 7,000 emeralds from local Indians.

And the real prize was still to come. The Spanish had heard of a mine with even larger, finer crystals. Muzo was its magical name, and even today Muzo is unlike any other mine in the world. For perhaps a thousand years it has consistently produced the biggest and best emeralds ever found. Muzo lay hidden from the conquistadores until 1558. But once in control, the Spaniards enslaved the Indians to mine emeralds on a grand scale.

Bogotá, emerald city: Wizards of street-smarts gather at a tense crossroads, where owners offer white envelopes of emeralds to swarming comisionistas, sales agents who then seek buys waiting in nearby buildings.

Exceedingly rare, a pre-Colombian emerald forms the body of a fanciful gold beast found in Panama. Spaniards looted thousands of emeralds from Indians. Hernán Cortés returned from Mexico in 1528 with a suite of carved emeralds for his bride. Legend holds that they were coveted by Isabella, Spain’s regent and wife of Charles V, and Cortés stock in court plummeted when he refused to give them up. He later lost them in a shipwreck.

Colombian maintains that emeralds belong to any Colombian who can mine them. The mining companies (Tecminas holds the principal Muzo lease) get ten-year leases from the government, but thousands of poor and armed guaqueros (treasure hunters) believe the leases are neither deserved nor valid.

Emeralds at Muzo are found in hydrother-mal veins of calcite buried within black shale. In order to foster employee honesty and enthusiasms, Tecminas practices a unique social program with its 250 workers-a system of pickups, in which each man is rewarded with one day a month at the face, the area actively being mined. As a dozer blade exposes emerald crystals, the whole crew races to the wall in a mad scramble to grab gemstones. After the free-for-all the mine representative, usually a member of one of the three families that control Muzo, keeps the biggest and best for the owners, leaving the rest as a goodwill bonus for the workers.

Coal mine, a series of raw cuts across the face of a promontory defined by the confluence of two mountain streams and a small river. Slick, powdery black shale covers everything and everyone. After a few minutes of digging, a miner is only recognizable as human by his white eyes and teeth.

Zambia and Zimbabwe account for some 25 percent of world emerald production. Noncommercial mining continues in a few countries, including Afghanistan, Madagascar, Australia, and Tanzania. Since the worldwide emerald business is almost all black market, no numbers are verifiable.

The Soviet Union has mined emeralds in the Ural Mountains for years but releases little data on the output. Pakistan, a new emerald producer, is already the fifth largest. The government actually works only two of its six sites, both located in Swat, which produce about 7,000 carats a month, worth $630,000 a year. Pakistan’s Gujar Kili is the most attractively situated emerald mine I visited, situated at 7,000 feet in Swat’s northern mountains. The mine, which is reachable only by hiking an hour and a half upstream and fording the Kotkai River three times is perched some 300 feet above the water.

" So soothing... is the mellow green color," wrote Pliny the Elder of smaragdus, a group of stones including emeralds, which grace third-century A.D. Roman earrings (below). A Byzantine pendant bears emeralds, pearls, and an agate. The stone adorning a first-century B.C. Egyptian double ring was assumed to be an emerald until a recent test identified it as green beryl.