[00:00.00]Unit six Text A
[00:02.09]第六单元 课文A
[00:04.18]Diamonds
[00:05.96]金刚石
[00:07.73]Diamonds are rare, beautiful, and also quite useful.
[00:10.81]金刚石是稀有物质，美丽，并且有使用价值。
[00:13.90]They are the hardest substance found in nature.
[00:16.27]金刚石是自然界所发现的最坚硬的物质。
[00:18.65]That means a diamond can cut any other surface.
[00:21.17]这意味着金刚石能够切割其他任何物体表面。
[00:23.69]And only another diamond can make a slight cut in a diamond.
[00:27.08]只有金刚石才能在金刚石上刻划很浅的痕迹。
[00:30.46]Diamonds are made from carbon.
[00:32.78]金刚石的成分是碳。
[00:35.11]Carbon is found in all living things,both plant and animal.
[00:38.30]碳存在于包括动物与植物在内的一切生物体中。
[00:41.48]Much of the carbon in the earth comes from things that once lived.
[00:44.96]地球上的大部分碳来源于曾是有生命的物体。
[00:48.43]Scientists know that the combination of extreme heat and pressure
[00:51.87]科学家认识到极高的温度和压力
[00:55.30] changes carbon into diamonds.
[00:57.67]使碳变成了金刚石。
[01:00.03]Such heat and pressure exist only in the hot,liquid mass of molten rock
[01:04.25]这样的高温与高压仅存在一地球内部深处
[01:08.47]deep inside the earth.
[01:10.65]炽热的液态熔岩中。
[01:12.83]It is thought that millions of years ago
[01:15.65]据认为，千百万年前
[01:18.47]this liquid mass pushed upward through cracks in the earth's crust.
[01:22.35]液态熔岩从地壳的裂缝间挤出地表。
[01:26.23]As the liquid cooled, the carbon changed into diamond crystals.
[01:29.86]当熔岩冷却时，其中的碳便成了金刚石晶体。
[01:33.49]There are only four areas where very many diamonds have been found.
[01:37.67]人们发现只有四个地区金刚石储藏量较多。
[01:41.85]The first known area was in India,
[01:44.37]第一个周知的地区在印度，
[01:46.89]where diamonds were found thousands of years ago.
[01:49.71]那里的金刚石是几千年前发现的。
[01:52.54]In the 1600's,
[01:54.77]16世纪初，
[01:57.00]travelers from Europe brought back these beautiful stones from India.
[02:00.63]来自欧洲的旅行家们将这些美丽的宝石从印度带回欧洲。
[02:04.26]Diamonds became very popular with the kings and queens of Europe.
[02:07.84]于是金刚石成为欧洲各国国王与王后的宠爱之物。
[02:11.42]In the 1720's, diamonds were discovered in Brazil.
[02:14.65]17世纪20年代巴西发现了金刚石。
[02:17.87]This discovery came at a good time, too.
[02:20.60]这次发现恰逢其时，
[02:23.33]India's supply of diamonds was finally running out after 2,500 years of mining the stories.
[02:28.47]因为在印度经过2500年的开采，金刚石的资源已接近枯竭。
[02:33.60]In the 1800's,
[02:35.48]18世纪初，
[02:37.36]two other important areas were found in Russia and South Africa.
[02:41.14]又发现了另外两个重要的金刚石产区：一个在俄国，另一个在南非。
[02:44.91]Today,most diamonds used in industry come from Russia.
[02:48.39]当今，多数工业用金刚石产自俄罗斯，
[02:51.86]Most diamonds used as gems come from South Africa.
[02:55.18]而制作珠宝用的金刚石大部分产于南非。
[02:58.49]Only 25 percent of all diamonds mined are good enough for cutting into gems.
[03:03.37]在所开采的全部金刚石中，仅有25%属于优质，适合加工成珠宝。
[03:08.24]Most of the diamonds in India were found in stream beds.
[03:12.07]在印度，大部分金刚石是在河床上发现的。
[03:15.89]People would pick up handfuls of gravel from the bottom of the streams
[03:19.38]人们从河底里拾起一把把砂砾，
[03:22.87]and sort out the diamonds.
[03:25.24]然后从中挑出金刚石。
[03:27.62]These diamonds were probably carried from where they were formed
[03:30.59]这些金刚石可能是从其形成的地方
[03:33.55] to India by great sheets of moving ice
[03:36.63]被大块移动的冰川带到印度的。
[03:39.72]that covered parts of the earth 20,000 years ago.
[03:42.38]二万年前地球的部分地区是被冰川覆盖着的。
[03:45.04]Most diamonds today are not found in stream beds, however.
[03:48.77]但是现在大部分金刚石已不是从河床上找到的，
[03:52.49]They are mined from rock formations deep inside the earth called pipes.
[03:56.32]而是从地下深称做火山筒脉的岩层结构中开采出来的。
[04:00.14]Scientists believe
[04:02.17]科学家相信，
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