钻石高考英语作文

高考英语作文 时间:2017-10-19 我要投稿
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  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.

  钻石

  钻石稀有,美丽,也很有用。它们是自然界中所发现的最硬的物质。这意味着钻石能切割其他任何表面,而且只有用钻石才能对其他钻石进行微小的切割。

  钻石是由碳形成的。所有的生物包括动物和植物,都含有碳。地球上的很多碳来自于曾经有生命的东西。

  科学家们知道,高热和高压共同作用会使碳变成钻石。这种高热和高压只存在于地球深处灼热的岩浆中。人们认为数百万年前这种岩浆从地壳的裂缝处向上涌出。当这种岩浆冷却后,碳就变成了钻石晶体。

  只有四个地区已发现有很多钻石。

  第一个知名的地区在印度。数千年前在这里就发现了钻石。在17世纪,欧洲的旅游者从印度带回了这些美丽的石头。钻石很受欧洲国王和王后们的喜爱。

  18世纪20年代,在巴西发现了钻石。这个发现来得也正是时候。印度的钻石经过2500年的开采,其储量将要耗尽。

  19世纪,在俄罗斯和南非又发现了两个重要地区。今天,大部分工业用钻石来自俄罗斯。大部分用作宝石的钻石来自南非。所有开采出来的钻石中只有25%适合于切割成宝石。

  在印度,大部分钻石是从河底里找到的。人们常常从河底拣起一把一把的砂砾,并挑选出钻石。可能是20,000年前覆盖地球部分地区的巨大冰块的移动把这些钻石从它们的形成地带到了印度。

  然而今天大部分钻石不是在河床里找到的。它们是从地球深处叫做管子的岩层中开采出来的。科学家们认为这些岩石组织是火山的组成部分,是当熔岩向上涌过地壳时形成的。他们把发现有钻石的坚硬岩石叫做蓝色脉岩,因为它的颜色有点蓝。人们把这种蓝色脉岩炸成大块的岩石,再用升降机把它们运到上面。然后很小心地把这些岩石压碎,以使钻石不受破坏。接着,压碎的岩石被送到冲洗桌上。在冲洗桌上,压碎的岩石从涂着厚厚油脂的板子上流过。因为钻石会粘在油脂上,所以岩石和泥浆流下桌子,而钻石留了下来。

  钻石被发现时并不很引人注目。它们是些灰色的、看起来光滑的小圆石。有经验的钻石矿工能立刻把钻石分辨出来,但也有一些人会带着一块不同寻常的圆石,直到好几个星期后才发现他们得到的是块钻石。

  印度18世纪钻石翡翠拖鞋多伦多不翼而飞

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