2010年中国人民大学考博英语真题

Part III. Reading Comprehension (30 paints)

The most valuable diamonds are large, individual crystals of pure crystallint carbon. Less perfect forms, known as 'boars' and 'carbonado' arc clustersof tiny crystals. Until diamonds are cut and polished, they do not sparkle licethose you sec on a ring--they just look like small, blue-grey stones.

In a rather crude form the cutting and polishing of precious stoneswas an art known to the Ancient Egyptians, and in the Middle Ages it became 1Lidcspreadiii north-west Europe. However, a revolutionarychange in the methods of cutting and polishing was made in 1476 when Ludwig VanBerquen of Bruges in Belgium invented the use of aswiftly 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 materialalready mentioned. It is also gimp to badly flawed or broken diamond crystals,useless as jewels, that are broken into powder for grinding purposes, theso-called `industrial' diamonds.

Diamond itself is the only material hard enough to cut and polishdiamonds--though recently, high-intensity light beams called lasers have beendeveloped which can bore holes in them. It may be necessary to split or cleavethe large stones before they arc cut and polished. Every diamond has a naturalline of cleavage, along which it may be split by a sharp blow with a cuttingedge.

A fully cut 'brilliant' diamond has 58 facets, or faces, regularly arranged.For cutting or faceting, the stones arc fixed into copper holders and heldagainst a wheel, edged with a mixture of Oil and fine diamond dust, which isrevolved at about 2,500 revolutions a minute. Amsterdamand Antwerp, in Hollandand Belgiumrespectively, have been the centre of the diamond cutting and polishingindustry for over seven centuries.

The jewel value of brilliant diamonds depends greatly on theircolour, or `water' as it is called. The usual colours of diamonds are white,yellow, brown, green or blue- Surrounding rocks and take on their color. thusblack ,red and even bright pink diamonds have occasionally been found.

The trade in diamonds Is not only in the valuable gem stones butalso 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, alsofor edging band saws for cutting stone. Diamond-faced tools are used forcutting and drilling glass and fine porcelain and for dentists' drills. Theyare used as bearings in watches and other finely balanced instruments. Perhapsyou own some diamonds without knowing it--in your wristwatch!

71. 'Carbonado' is the name given to

A) only the very best diamonds B)lumps of pure carbon

C) Spanish diamonds D)diamonds made up of many small crystals

72. The art of cutting and polishingprecious stones remained crude until

A) the fourteenth century B) the fifteenth century

C)the sixteenth century D) the seventeenth century

73. During faceting, diamonds are held incopper holders

A) to facilitate accurate cutting B) to make them shine more brilliantly

C) so that they can revolve more easily D) as a steel holder might damage thediamond

74. The value order of `water' in diamond, _

A) is more important than their colour B)ranges from blue-white upwards

C) ranges from blue-white downwards D) has never been reliably established

75. Industrial diamonds are used

A) for a wide range of purposes B) mainly for dentists' drills

C) for decoration in rings and watches D)principally in mass-produced jewellery

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