Учебное пособие Иркутск 2006 Рецензент

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Spinel

Spinel came principally from traditional sources, including both primary and secondary deposits in Southeast Asia (Burma, Cambodia, and Thailand) and secondary (alluvial) deposits in Sri Lanka. Some material also came from Tanzania and Brazil. Characterization of material from old and some new localities led to a better understanding of the causes of color and the range of properties among gem spinels. For example, investigators saw the first description of color-change spinel. Anderson, Jackson, and Schmetzer and Bank reported the properties of gem-quality, zinc-bearing gahnite and gahnospinel from Nigeria and Sri Lanka. In the mid-1980s, demand for red spinel increased dramatically as it gained appreciation as a medium-priced red stone. One of the newest and most promising developments has been the discovery of exceptionally large, transparent pink spinels from the Pamir Mountains of the former Soviet Union.

Amethyst and Citrine

Brazil was the major producer of fine amethyst and citrine. Amethyst occurs in both igneous and sedimentary geologic environments, principally in the states of Paraiba, Goias, Ceara, Bahia, Minas Gerais, and Rio Grande do Sul. Epstein described the occurrence of amethyst in fractures in quartzite in Maraba, the alluvial deposit at Pau d’Arco, and the mining of amethyst geodes from basalt near Santa Maria and at Irai. Amethyst is also produced in Uruguay in colors comparable. New were major deposits of intensevely colored, reddish purple amethyst in Zambia. As is the case in many Third World countries, the rough crystals must be purchased through a state agency, in this instance known as Mindico. A new locality near Port Hedland in Western Australia has also produced fine material. The great majority of citrine available was actually heat-treated amethyst from Brazil. One of the most interesting materials to emerge in the gem market was bicolored amethyst-citrine (“ametrine”). Although reports speculated that these stones were produced by treatment, crystals displaying both colors have been confirmed from a deposit known as La Gaiba, in the Rincon del Tigre region of Bolivia, near the border with Brazil.

Topaz

Topaz production involved three distinct color groups: colorless and light blue topaz used for treatment, golden yellow to “sherry” red Imperial topaz, and pink topaz. Brazil, Sri Lanka, and Nigeria produced millions of carats of colorless to light blue topaz for treatment by irradiation and annealing to create various intensities of blue. Brazil continues to be known for its famous Imperial topaz mines in the vicinity of Ouro Preto, in Minas Gerais. First documented in the 1700s, these mines are the only source of material in this attractive range of orange-to-red colors.

Small quantities of fine pink topaz were mined from the Katlang district of Pakistan in a deposit that produces material ranging from colorless to light brown, and from pale pink to deep pink. Other topaz deposits were found about 20 km from Katlang, at Shakertangi. As more of the mountainous area of northern Pakistan is explored, it is likely that additional deposits will be found. The gem potential of that region seems high. Even with the increased mining in Pakistan, most of the pink topaz on the market was produced by heat-treating of yellow topaz from Brazil.

Tourmaline

Brazil is by far the most important source of gem tourmaline, which occurs there in an astonishing range of colors. The most productive districts are principally in Minas Gerais. Perhaps the most exciting tourmaline discovery was made in the late 1980s in another area of Brazil, the state of Paraiba, where the mine has produced significant amounts of tourmaline in a variety of unusual violet, blue, and green colors.

Commercial amounts of tourmaline also continued to come from long-recognized sources such as Afghanistan, Namibia, Sri Lanka, the United States, and Transbaikal (Russia). Particularly important discoveries of tourmalines of unusual color and composition were made in East Africa, specifically in Kenya, Zambia, and Tanzania. Nigeria is now producing interesting bicolored tourmaline, with commercial amounts of other colors also coming from Mozambique. Madagascar continued to produce a broad range of tourmaline species and varieties, and is experiencing an increase in exploration and mining activity.

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Famous diamonds

The Hope

Weight: 45.52 carats

Color: dark blue

Clarity: reportedly flawless

Cut: oval brilliant

Source: India

Asked to name a famous diamond, most Americans would say, “the Hope”. Jean Tavermier, a French adventurer and gem merchant, discovered the 112-ct. rough diamond in India in 1642 (and called it the Tavemier Blue). Louis XIV of France gave him a title and a fortune for it. Legend says wild dogs killed Tavemier on another trip to India. The French King had the diamond recut to a 69.03-ct. heart shape and shortly later died of smallpox. Stolen from the treasury during the French Revolution, the diamond changed hands several times before becoming the property of Henry Philip Hope in London in 1830. He died childless, and the Hope Diamond passed to a distant relative, Francis Pelham Clinton, on condition that he never sell it and change his last name to Hope. As Lord Francis Hope, he gambled his way to bankruptcy (his wife, who left him for another man, blamed the diamond for the bad luck). Lord Hope sold the diamond in 1906 to pay his debts.

According to legend, the Hope then belonged to a French broker (who committed suicide), a Russian prince (stabbed to death), a Greek jeweler (thrown over a precipice), and finally Pierre Cartier. He sold it in 1911 to Evalyn Walsh McLean. Cartier appears to have cited the diamond’s history, inventing the “Hope curse,” to pique Mrs. McLean’s interest. Mrs. McLean, leader of Washington society, often treated the famous diamond like a toy, keeping it in the cushions of her sofa, letting her Great Dane wear it, allowing hospitalized soldiers to play catch with it, and lending it to friends. She never considered it unlucky.

But at the age of nine, Mrs. McLean’s son died in a car accident. Her husband got into political trouble, divorced her, and died insane. Her daughter committed suicide. Evalyn McLean became addicted to morphine and died in 1947. Two years later, Harry Winston bought the Hope Diamond and sent it on tour to raise money for charity. In 1958, he donated it to the Smithsonian Institution. When you’re in Washington, DC, visit the Smithsonian for a look at the Hope Diamond. No jeweler should miss the chance.

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Famous diamonds

The Arcots

Weight: 57.35 carats (combined)

Color: unrecorded

Clarity: unrecorded

Cut: pear-shape brilliant

Source: India

In 1777, Azim-ub-duala, Nabob of Arcot, in southeast India, gave two beautifully matched diamonds to England’s Queen Charlotte, wife of George III. When she died in 1818, her will specified the diamonds were to be sold to raise money for the support of her four daughters. The Crown Jewelers, Rudell, Bridge & Co., bought them and held them until 1837, when Bridge died and the firm was sold. They were then bought by the Marquis of Westminster, who had them mounted in earrings as a birthday present for his wife.

The Arcots were worn as earrings until 1930, when the Parisian jeweler Lacloche mounted them, along with a 32-carat brilliant and 1,421 smaller diamonds, in the Westminster Tiara. In June 1959, William Grosvenor, third Duke of Westminster, had the tiara auctioned off by Sotheby’s. Harry Winston bought it, and had the Arcots reset in earrings once again. They are now in a private collection in Texas.

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Famous diamonds

Marie Antoinette necklace

The story of the Marie Antoinette necklace begins when the French Crown Jewelers made a necklace of 647 fine diamonds for Madame Du Barry, the King’s mistress. When he suddenly died, the jewelers, desperate to recover their investment, tried unsuccessfully to peddle their masterpiece at every court in Europe. Meanwhile, the “Countess” de la Motte-Valois peddled herself. She had little besides the ancient Valois name, but she wanted the life-style felt went with it. Loitering at the edges of the court, she took up with the Cardinal de Rohan, scion of one of France’s leading families. Eager to be a power-wielding prime minister like Cardinals Richilieu and Mazarin, he had made the mistake of insulting Marie’s mother. Knowing how badly he wanted to regain favor, the countess told him she knew the Queen wanted to make up, too, and somehow conned him into buying the necklace; if he paid for it, she said, the Queen would reimburse him.

The Cardinal jumped at the chance and made a down payment, signing a note for the rest. He gave the necklace to a “royal messenger”. Weeks stretched into months; the Cardinal waited for the Queen to show her gratitude; the jewelers pressed for payment, and the Countess made excuses. Her husband was in London, selling the ill-gotten stones. Eventually, the jewelers went to the Queen. Assuming the Cardinal had used her name to get the necklace, she had him arrested. After a public confrontation, he was freed and the Countess was jailed, but she escaped to England and wrote a lurid set of “memoirs” which fanned the revolutionary fire already smoldering in France. The affair may not have caused the revolution, but it was a cause celebre for the antiroyalists.

The jewelers went broke. The Countess was killed trying to escape what she thought was a gang sent to drag her back to France. Louis XVI and Marie Antoinette were guillotined. The Cardinal retired to his estate and performed charitable works until his death. The Duke of Sutherland wound up with the 22 largest stones; other were bought by the Duke of Dorset. The fate of the rest remains a mystery.

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Blog

Учебное пособие Иркутск 2006 Рецензент

Spinel

Topaz

Tourmaline