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 hand rock in which diamonds are found is called blue ground.
可是，今天绝大多数的钻石都不是在河床上找到的；今天的钻石都是从地球内部很深的地方，从被称为岩筒的管状矿脉的矿井中开采出来的。专家们认为这些岩筒都是火山的一部分，是在溶岩从地壳的裂缝中挤压到上面来的时候形成的。里面含有钻石的坚硬的矿石叫蓝脉矿。
