Page:The New International Encyclopædia 1st ed. v. 06.djvu/241

* DIAMOND. the value abnormally. The value ordinarily in- crea.se.s in a ratio increasing with the weight, but this rule does not hold good for the largest stones, the prices of which cannot be fixed. Dia- monds in the rough generally average $8 to $15 the carat for the run of the mine. Eem.rkable DiAiioNns. The most valuable gems, among which there are some exceeding 100 carats in weight, are generally owned by royal families or are treasured by governments as State jewels. One of the largest is the Orloff, owned by the Czar of Russia, which weighs 105 carats, and is cut in I'ose form. Its origin is doubtful: according to one account, it was stolen from a Brahman temple in India, while anoiher indicates that it was owned by Xadir Shah of Persia, and came after his death into the hands of an .rnienian merchant. In 1772 it was pur- chased by the Empress Catharine 11., at a price said to have been .$450,000, besides an annuitv of $4,000 and a Russian title. The Kohi-nflr, weighing lOiSi carats, and owned by the royal family of England, was found, according to legend, in India long before the Christian Era. After having been handed down through a long line of Indian princes, it was seized during the British invasion of the Punjab, and carried to England. The stone is said to have weighed originally 794 carats, having been reduced to its present size by repeated cutting. The Regent or Pitt diamond in the Louvre in Paris, weighs 136 carats, and is valued at $2,500,000. It is perhaps the finest of large brilliants. The Hope diamond, weighing 44I4 carats, is a beauti- ful blue stone, valued at $125,000. A light green diamond of 481^2 carats, in the Green Vault at Dresden, and a red diamond of 10 carats, among the crown jewels of Russia, are unique specimens. Among the most valuable stones found in recent times are the Victoria, weighing 180 carats, which was purchased by the Xizain of Hyderabad: the De Beers, weighing 225 carats: and the Tifl'any, weighing 125 carats. DiAMOND-CuTXrxG. The art of diamond-cut- ting was not developed until the middle of the fifteenth century, although crude methods of polishing were in use long before that time. About 1470 a guild of lapidaries was established at Bruges, under the direction of Louis de Ber- quem, who is thought to have been the first to devise a regular plan for the arrangement of facets, so as to increase the color effects in gems. Other guilds were soon founded in Antwerp and Amsterdam, and these cities rapidly gained pre- eminence in the industry, a position they still maintain. London, the market for rough stones, is a small competitor, while Paris and Xew York are unimportant, except for the sale of gems. In diamond-cutting, the operations are per- formed with the single object of producing the most valuable gem from a crude stone. The apparatus used is simple, but its manipulation requires both skill and experience. In the first place, the stone must be examined carefully to determine its shape, color, and the possible pres- ence of flaws, as these features will govern the operation of cutting. If the shape is such that it cannot be reduced readily to one of the usual forms, the stone may be divided into two or more parts by taking advantage of the natural cleavasze. The diamond is cemented to a wooden holder and a steel blade is applied in a direction 201 DIAMOND. parallel to an octahedral fa<;e. A sharp blow upon the back of the blade is sufficient to accom- plish the cleaving. The next jjrocess (liruting) brings out the facets. Two rough stone-:, fixed at the end of holders, arc held in either hand of DIAMOXD-CUTTIXG. Figs. 1-5— the Brilliant: land 2, fundamental torm; 3.4.5, side, top, and back views of tbe cutting. Figs. and 7, top and side views of the Rose cutting. Fig. 8, view of the Briolette cutting. the operator, who presses them against each other, at the same time giving them a rubbing motion. The friction wears away the surfaces gradually until they coincide in position to two of the facets. The diamonds are then cemented in new positions, and the operation is continued. The waste particles of dust are collected and used in the final process of polishing. For this the apparatus consists of a small disk of spongy cast-iron, turning on a vertical spindle at a speed of 2000 to .3000 revolutions per minute. The stone, imbedded in the apex of a metallic (lead-tin) cone is held by a clamp against the surface of the disk, which is smeared from time to time with a mixture of olive oil and dianumd- dust. This operation requires constant atten- tion, as the stone may be permanently damaged b_y over-heating. Of the several forms in which diamonds are cut, the briUianI is the favorite. It is derived from the fundamental octahedron and requires, when perfect, 58 facets. In the middle is an octagonal facet called the 'table,' which is sur- rounded by 32 smaller facets, reaching to the line of union (girdle) between the upper and lower portions. On the lower portion there are 24 facets symmetrically arranged around the 'culet.' The rose form is used for thin stones. It consists of a number of triangular facets, the apices of which meet in the crown, and whose bases are supported by a second row of facets extending to the girdle. The lower part is per- fectly flat. In the briolette the stone is cut into triangular facets, but the form is pear-shaped and there is no girdle. Bii!i,iOGK.PHY. Kunz. Gems and Precious Stoties (Xew York. inOO) : Streeter, Precions f^tones nnd Gems (London, 1804) : Streeter. The Great Diamonds of the World (London. 1882) ; Church, Precious Stones (London, 1883) ; De