59 The World's Hardest Substance

The diamond is the hardest natural substance in the world. What causes this super-hardness? Pressure and heat are the answers. The pressure has to be over two million pounds. That’s per square inch. Much heat is required too. Experts say over 5,000 degrees. To make a diamond, one more thing is needed. This is black carbon. Pressure, heat, and carbon combine. They create a sparkling diamond. The very best are colorless. Pale blue stones—very rare—are high quality too.

Where do most diamonds come from? Over 97 percent come from Africa. The first diamond in Africa was not found by miners. Children found it, in 1866. They were playing in a shallow stream. One picked up a “pretty pebble.” The “pebble” was placed on the mantle of the fireplace. It was soon forgotten. Much later, a guest noticed it to sparkle. He urged the farmer to have the stone looked at. He did. He took it to a small expert in town. The “pebble” proved to be a diamond worth $25,000. That was a fortune in those days. To date, the mines in Africa have produced over 1 billion dollars’ worth of diamonds.

Not all diamonds are found in Africa. Our hemisphere produced diamonds too. Brazil was a big producer in earlier times. The famous gem the Star of the South was found in Brazil in 1853.

The gem The President Vargas was found more recently in Brazil. This was in 1938. A poor prospector found the stone. It was in the San Antonio River. It weighed 726.6 carats. The man sold the stone for $10,000 to a local broker. The broker almost immediately resold it. He got about $25,000. What a nice guy!

59 世界上最坚硬的物质

钻石是世界上最坚硬的天然物质。是什么造成了这种超高硬度呢？答案是压力和热量。压力必须超过两百万磅，是每平方英寸的压力。也需要大量的热量，专家称要超过5000度。要形成钻石，还需要一样东西，那就是黑色的碳。压力、热量和碳结合在一起，就形成了闪闪发光的钻石。品质最佳的钻石是无色的，淡蓝色的钻石——非常稀有——品质也很高。

大多数钻石来自哪里呢？超过97%的钻石来自非洲。非洲的第一颗钻石不是由矿工发现的，是孩子们在1866年发现的。他们在一条浅溪里玩耍，其中一个捡到了一块“漂亮的鹅卵石”。这块“鹅卵石”被放在壁炉的台面上，很快就被遗忘了。很久以后，一位客人注意到它闪闪发光，他力劝农夫去鉴定这块石头。农夫照做了，他把石头带到镇上的一位小专家那里。结果证明这块“鹅卵石”是一颗价值25000美元的钻石，在当时这是一笔巨款。到目前为止，非洲的钻石矿已经产出了价值超过10亿美元的钻石。

并非所有钻石都在非洲被发现，我们所在的半球也产钻石。巴西在早期是一个重要的钻石生产国，著名的“南方之星”宝石于1853年在巴西被发现。

“Vargas总统”宝石是最近在巴西被发现的，时间是1938年。一位贫穷的勘探者在圣安东尼奥河发现了这块石头，它重726.6克拉。这个人以10000美元的价格把石头卖给了当地的一个经纪人，这个经纪人几乎立刻就转卖了它，得到了大约25000美元。真是个不错的家伙！