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Regent Diamond PDF Print E-mail
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Monday, 29 October 2007

Regent diamond. Originally known as the Pitt diamond, this 410-carat diamond was one of the last large stones found in India; it is said to have come from the Parteal Mines on the Kristna River about 1701. It was sold to Governor Thomas Pitt, of Ft. George, Madras, who was the great grandfather of William Pitt of American Revolutionary fame, for approximately $100,000. He sent it lo England and had it cut into a 140.50-carat cushion-shaped brilliant that measured 1-1/16 inches long, 1 inch wide, and 3A inch deep. The stone, which has but one very small imperfection, is today considered one of the finest and most brilliant of (he known large Diamonds. In 1717, it was sold to the Duke of Orleans, then Regent of France, for about $500,000; since it has been known as the Regent diamond. It was set in the crown of Louis XV, and Marie Antoinette is said to have worn it in a large black-velvet hat. It disappeared in the French jewel rob­bery of 1792 but was found again in a Paris garret and was pledged for money that helped Napoleon in his rise to power. He had it mounted in the hilt of the sword that he carried that time, at his coronation. When Napoleon went into exile, Marie Louise, his second wife, carried the Regent to the Chateau de Blois. Later, however, her father, the Emperor of Austria, re­turned it to France and it again be­came part of the French Crown Jewels; many of these were sold at auction in 1887, but the Regent was reserved. In 1940, when the Ger­mans invaded Paris, it was again sent to the chateau country, this time to Chambord, where it was secreted behind a stone panel. After the War, it was returned to Paris and placed on display in the Apollon Gallery of the Louvre Museum. Also sometimes known as the Millionaire diamond.

 
Regale of France Diamond PDF Print E-mail
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Monday, 29 October 2007

Regale of France diamond. A legen­dary stone, said to have been as large as a "bird's egg." St. Louis (King I ouis IX, of France), according to the story, disguised as a poor pilgrim, brought the stone as an offering to Ihe Shrine of St. Thomas a Becket, in England, and received in return a small leaden figure of St. Thomas. Ihe whereabouts of the diamond today is not known.

 
refractometer PDF Print E-mail
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Monday, 29 October 2007

refractometer (re'-frak-tom"-ehter).An optical instrument for measuring the refractive index of a gemstone. It is useful for detecting diamond sub­stitutes, with the exception of a few materials whose refractive indices, like that of diamond, are above the limits of the instrument; e.g., GGG, synthetic rutile, strontium titanate, zircon, YAG. See refractive index, re­fraction.

 
refractive index PDF Print E-mail
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Monday, 29 October 2007

refractive index. A measure of the amount a light ray is bent as it enters or leaves a gemstone, expressed by numerals. It is the ratio of the veloc­ity of light in air to its velocity in a given substance. It is also the ratio of the sine of the angle of incidence to the sine of the angle of refraction. Other factors being equal, the higher the R.I., the greater the brilliancy. The refractive index of diamond is 2.417 for sodium light (5890 A). See CRITICAL ANCLE, REFRACTOMETER, REFRACTION, BRILLIANCY, CRITICAL ANCLE CONE, ANCLE OF RE­FRACTION.

 
refraction PDF Print E-mail
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Monday, 29 October 2007

refraction. The bending of light rays. The deflection from a straight path suffered by a ray of light as it passes obliquely from a medium of one op­tical density to another medium of different optical density, as from air into water and from air into a gem-stone. The degree of bending is re­lated to the change in the velocity of light and the angle at which the light impinges. See anisotropic, isotropic,

ANOMALOUS DOUBLE REFRACTION, POLARISCOPE, REFRACTIVE INDEX, ANGLE OF REFRACTION, OPTICALLY DENSE.

 
reflectivity meter PDF Print E-mail
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Monday, 29 October 2007

reflectivity meter. An electronic de­vice for measuring the relative ability of a surface to reflect radiant energy. Relative reflectivity depends on R.I., flatness, quality of polish, and the cleanness of the surface. Since reflec­tivity meters are not limited by the 1.81 maximum reading on a conven­tional refractometer, they are useful for stones above this limit. Results are not always repeatable or accu­rate. Reflectivity meters do not mea­sure birefringence. The "Gemeter," "jeweler's Eye," and the "Re-dex" are reflectivity meters presently avail­able.

 
reflection PDF Print E-mail
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Monday, 29 October 2007

reflection. The returning or rebound­ing of light rays which strike a sur­face. The angle of reflection is equal to the angle of incidence. Some of the light that strikes the surface of a stone is reflected from the surface and some is refracted into the stone which in turn may be internally re-

 
Red Diamond PDF Print E-mail
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Monday, 29 October 2007

red diamond. The rarest of all fancy-colored Diamonds. However, the term is often used to mean red-brown or rose-colored stones. Dia­monds of the full red color of ruby are rare.

 
Red Diamond PDF Print E-mail
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Monday, 29 October 2007

Red diamond. Discovered in 1927 at the Lichtenburg diggings of South Af­rica, the 33-carat black bort rough sold for only $160. Originally thought to be just a piece of bort to be used as powder for polishing. The buyer, Mr. Houtakker, took the ad­vice of Sir Ernest Oppenheimer and sent the rough to Amsterdam for cut­ting. There, a flawless blood-red, emerald-cut stone of 5.05 carats was cut from the center of the rough. The Red diamond had many adventures and was first sold in 1947 for an un­known price. In 1968, it was re­ported to be owned by a private col­lector in New York.

 
Red Cross Diamond PDF Print E-mail
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Monday, 29 October 2007

Red Cross diamond. Canary yellow in color and weighing 375 carats in the rough, this South African dia­mond was cut into a 205-carat square cut. A "Maltese cross effect" can be seen through the table as a result of cutting. The London Dia­mond Syndicate presented the stone to the British Red Cross Society and the order of St. John of Jerusalem in 1918. Later in the same year, it was sold to an undisclosed buyer on be­half of the Red Cross at the London auction house of Christie, Manson & Woods for £10,000. For many years it was rumored to have belonged to a royal family in Europe. Sometime prior to 1950, the Red Cross was ac­quired by a Saudi Arabian who sold it at auction in Geneva in November 1973 to an unknown buyer. The stone is now privately owned and deposited in Switzerland where it is presently for sale.

 
recutting PDF Print E-mail
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Monday, 29 October 2007

recutting. The process of refinishing a polished stone in order to improve its clarity grade, proportions, to re­pair damage or to improve its overall appearance. Also used to update or modernize an old style cut.

 
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