Famous Diamonds, Use and Meaning
The diamond is the most important of the gem stones. Its value depends upon its hardness, its brilliancy, which is due to its high index of refraction, and to its ”fire,” which is due to its strong dispersion of light into the prismatic colors. In the most valuable stones are those which are flawless and colorless or posses a “blue-white” color. A faint straw-yellow color, which diamond often shows, detracts much from its value. Deep shades of yellow, red, green or blue are greatly prized and fine stones of these colors bring very high values.
The diamond is cut by first cleaving off any undesirable or flawed portions of the crystal and then grinding facets upon it by use of diamond powder. The crystal is fixed at the end of a stick by means of soft solder, leaving the part projecting which is to be cut. A circular plate of soft iron is then charged with diamond dust, and this by its revolution grinds and polishes the stone. Most diamonds are cut into the from knows as the brilliant (see Fig. 209) This is a stone cut with a large eight-sided facet on top and a series of small inclined faces around it. The lower half consists of steeply inclined faces giving the stone on this side a pyramidal shape. The depth of a brilliants it nearly equal to its breadth, and it, therefore, can only be cut from a thick stone. Thinner stones, in proportion to the breadth, are cut into what is unknown as the rose diamond. This is a stone a stone which has its upper surface covered with small triangular facets. Its lower surface may be one plane face, or the cutting of the upper half may be duplicated. With exceptional –aped stones other cuttings are used.
The value of a cut diamond depends upon its color and purity, upon the skill with which it has been cut and upon its size. A once carat stone weighs 200 milligrams, and if cut in the form of a brilliant would be 6.25 millimeters in diameter and 4 millimeters in depth. A two- carat stone of the same quality would have a value three or four times as great.
Famous Stones: The older famous diamonds include the following: The Kohinoor, weighing 106 carats, is one of the crown jewels of Great Britain; the Regent or Pitt, weighing 136 carats, belonging to France; the Orloff, which is mounted in the Russian imperial scepter, weighs 193 carat; the Star of the South, weighing 125 carats, is said to be in India.
Large stones found more recently is South Africa include the following: the Victoria or Imperial, which weighed 457 carats when found, and 230 when cut. It was, however later recut its present weight being 180 carat. The Stewart weighed before and after cutting 288 and 120 carats respectively. The Tiffany diamond, which is of a brilliant yellow color, weighs 125 carats. The Colenso diamond, presented to the British Museum in 1887 by JOHN Ruskin, weighs 129 2/3 carats. The Excelsior diamond, found at Jagersfontein in 1903, is now known as the Jubilee, and weighs 239 carats. The Cullinan or Premier diamond was found a t the Premier Mine, Tranvall, and was the largest stone ever found, weighing 3024 carats or 1.7 pounds troy, and measured 4 by 2 ½ 2 inches. This stone was presented to King Edward VII by the Tranvall Government and has been cut into 9 large stones the larger ones weighing 516, 309, 92 and 62 carats respectively, and into 96 smaller brilliants.
Name. the name diamond comes from the Greek word adams, meaning “invincible”.
Use. In addition to its wide use as a gem, the diamond is extensively used as abrasive, Crustal fragments are used to cut glass. The fine powder is employed in grinding and polishing diamonds and other stones. The noncrystalline, opaque varieties, especially that known as carbonado are used in the bits of diamond drills, These drills are frequently employed in mining operations to explore the rocks and to determine the position and size of ore bodies. Recently the diamond has been used in wiredrawing and in the making of tungsten filaments for electric lights.
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