鉆石高考英語作文

　　Diamonds are rare, beautiful, and also quite useful. They are the hardest substance found in nature. That means a diamond can cut any other surface. And only another diamond can make a slight cut in a diamond.

　　Diamonds are made from carbon. Carbon is found in all living things, both plant and animal. Much of the carbon in the earth comes from things that once lived.

　　Scientists know that the combination of extreme heat and pressure changes carbon into diamonds. Such heat and pressure exist only in the hot, liquid mass of molten rock deep inside the earth. It is thought that millions of years ago this liquid mass pushed upward through cracks in the earth’s crust. As the liquid cooled, the carbon changed into diamond crystals.

　　There are only four areas where very many diamonds have been found.

　　The first known area was in India, where diamonds were found thousands of years ago. In the 1600’s, travelers from Europe brought back these beautiful stones from India. Diamonds became very popular with the kings and queens of Europe.

　　In the 1720’s, diamonds were discovered in Brazil. This discovery came at a good time, too. India’s supply of diamonds was finally running out after 2,500 years of mining the stones.

　　In the 1800’s, two other important areas were found in Russia and South Africa. Today, most diamonds used in industry come from Russia. Most diamonds used as gems come from South Africa. Only 25 percent of all diamonds mined are good enough for cutting into gems.

　　Most of the diamonds in India were found in stream beds. People would pick up handfuls of gravel from the bottom of the streams and sort out the diamonds. These diamonds were probably carried from where they were formed to India by great sheets of moving ice that covered parts of the earth 20,000 years ago.

　　Most diamonds today are not found in stream beds, however. They are mined from rock formations deep inside the earth called pipes. Scientists believe that these are parts of volcanoes that were formed when molten rock pushed upward through the earth’s crust. The hard rock in which diamonds are found is called blue ground, because it is somewhat blue. The blue ground is blasted into large pieces of rock which are carried to the surface by elevator. Then the rocks are carefully crushed so that the diamonds are not destroyed. Next, the crushed material is taken over to washing tables. Here, it flows over boards thickly coated with grease. Since diamonds stick to grease, they are left behind by the rocks and mud which flow down the tables.

　　Diamonds, as they are found, do not look very impressive. They are gray, greasy-looking pebbles. Experienced diamond miners can tell a diamond immediately. But some people have carried around an unusual pebble for weeks before finding out that they had got a diamond.

　　鉆石

　　鉆石稀有，美麗，也很有用。它們是自然界中所發(fā)現(xiàn)的最硬的物質(zhì)。這意味著鉆石能切割其他任何表面，而且只有用鉆石才能對其他鉆石進行微小的切割。

　　鉆石是由碳形成的。所有的生物包括動物和植物，都含有碳。地球上的很多碳來自于曾經(jīng)有生命的東西。

　　科學家們知道，高熱和高壓共同作用會使碳變成鉆石。這種高熱和高壓只存在于地球深處灼熱的巖漿中。人們認為數(shù)百萬年前這種巖漿從地殼的裂縫處向上涌出。當這種巖漿冷卻后，碳就變成了鉆石晶體。

　　只有四個地區(qū)已發(fā)現(xiàn)有很多鉆石。

　　第一個知名的地區(qū)在印度。數(shù)千年前在這里就發(fā)現(xiàn)了鉆石。在17世紀，歐洲的旅游者從印度帶回了這些美麗的石頭。鉆石很受歐洲國王和王后們的喜愛。

　　18世紀20年代，在巴西發(fā)現(xiàn)了鉆石。這個發(fā)現(xiàn)來得也正是時候。印度的鉆石經(jīng)過2500年的開采，其儲量將要耗盡。

　　19世紀，在俄羅斯和南非又發(fā)現(xiàn)了兩個重要地區(qū)。今天，大部分工業(yè)用鉆石來自俄羅斯。大部分用作寶石的鉆石來自南非。所有開采出來的鉆石中只有25%適合于切割成寶石。

　　在印度，大部分鉆石是從河底里找到的。人們常常從河底揀起一把一把的砂礫，并挑選出鉆石。可能是20，000年前覆蓋地球部分地區(qū)的巨大冰塊的移動把這些鉆石從它們的形成地帶到了印度。

　　然而今天大部分鉆石不是在河床里找到的。它們是從地球深處叫做管子的`巖層中開采出來的。科學家們認為這些巖石組織是火山的組成部分，是當熔巖向上涌過地殼時形成的。他們把發(fā)現(xiàn)有鉆石的堅硬巖石叫做藍色脈巖，因為它的顏色有點藍。人們把這種藍色脈巖炸成大塊的巖石，再用升降機把它們運到上面。然后很小心地把這些巖石壓碎，以使鉆石不受破壞。接著，壓碎的巖石被送到?jīng)_洗桌上。在沖洗桌上，壓碎的巖石從涂著厚厚油脂的板子上流過。因為鉆石會粘在油脂上，所以巖石和泥漿流下桌子，而鉆石留了下來。

　　鉆石被發(fā)現(xiàn)時并不很引人注目。它們是些灰色的、看起來光滑的小圓石。有經(jīng)驗的鉆石礦工能立刻把鉆石分辨出來，但也有一些人會帶著一塊不同尋常的圓石，直到好幾個星期后才發(fā)現(xiàn)他們得到的是塊鉆石。

　　印度18世紀鉆石翡翠拖鞋多倫多不翼而飛

【鉆石高考英語作文】相關文章：

1.高考英語作文

2.高考英語作文

3.高考英語作文

4.高考英語作文

5.英語作文高考

6.鉆石作文900字

7.高考英語作文范文

8.桂林高考英語作文