This is repeated three times, until at last the pure copper is left by itself.

这样的流程需要重复三次，直到最后剩下纯铜。

It was fine ore, almost pure copper; he must do something with it, and not let everything slide.

那是精矿，几乎是纯铜；他必须用它做点什么，不能让一切都溜走。

19. Copper ore contains sulfur, and heap roasting was a way to burn away the sulfur in the copper-so they'd be left with something closer to pure copper.

铜矿含有硫磺，堆烧是烧去铜里面硫磺的一种方法，所以留下的近乎于纯铜。

On the shores of Lake Superior in North America, lumps of pure copper are found in the rocks; but in Cornwall , and in Australia, and in many other places, we find copper as an ore.

在北美苏必利尔湖岸边的岩石中，人们可以看到成块的纯铜。然而，无论是在康沃尔、澳大利亚还是其他众多地区，铜都以矿石的形式存在。

Means, no doubt, that the ore must be more than commonly rich at the farther end of the tract; they are getting out pure heavy copper, and keeping to that end all the time.

毫无疑问，这意味着该区域的另一端的矿石一定比通常情况下更丰富；他们正在生产纯重铜，并一直坚持这一目标。