The most valuable diamonds are large, individual crystals of pure crystal lint carbon. Less perfect forms, known as “boars” and “carbonado” are clusters of tiny crystals. Until diamonds are cut and polished, they do not sparkle like those you see on a ring — they just look like small, blue-grey stones.
In a rather crude form the cutting and polishing of precious stones was an art known to the Ancient Egyptians, and in the middle Ages it became widespread in north-west Europe. However, a revolutionary change in the methods of cutting and polishing was made in 1476 when Ludwig Van Berquen of Bruges in Belgium invented the use of a swiftly revolving wheel with its edge faced with fine diamond powder. The name “boast” is given to this fine powder as well as the natural crystalline material already mentioned. It is also gimp to badly flawed or broken diamond crystals, useless as jewels that are broken into powder for grinding purposes, the so-called “industrial” diamonds.
Diamond itself is the only material hard enough to cut and polish diamonds — though recently, high-intensity light beams called lasers have been developed which can bore holes in them. It may be necessary to split or cleave the large stones before they are cut and polished.
Every diamond has a natural line of cleavage, along which it may be split by a sharp blow with a cutting edge. A fully cut “brilliant” diamond has 58 facets, or faces, regularly arranged. For cutting or faceting, the stones are fixed into copper holders and held against a wheel, edged with a mixture of Oil and fine diamond dust, which is revolved at about 2,500 revolutions a minute. Amsterdam and Antwerp, in Holland and Belgium respectively, have been the centre of the diamond cutting and polishing industry for over seven centuries.
The jewel value of brilliant diamonds depends greatly on their colors, or “water” as it is called. The usual coolers of diamonds are white, yellow, brown, green or blue. Surrounding rocks and take on their color, thus black, red and even bright pink diamonds have occasionally been found.
The trade in diamonds is not only in the valuable gem stones but also in the industrial diamonds mentioned above. Zaire produces 70% of such stones. They are fixed into the rock drills used in mining and civil engineering, also for edging band saws for cutting stone. Diamond-faced tools are used for cutting and drilling glass and fine porcelain and for dentists’ drills. They are used as bearings in watches and other finely balanced instruments. Perhaps you own some diamonds without knowing it — in your wristwatch!
1. “Carbonado” is the name given to（ ）.
2. The art of cutting and polishing precious stones remained crude until（ ）.
3. During faceting, diamonds are held in copper holders（ ）.
4. The value order of water in diamond（ ）.
5. Industrial diamonds are used（ ）.
