Next, by focusing on a super radioactive ore called pitchblende, the Curies realized that uranium alone couldn't be creating all the radiation.

接下来， 通过专注于做沥青铀矿的超级放射性矿石，居里夫妇意识到铀本身不可能产生所有的辐射。

By 1902, the Curies had extracted a tenth of a gram of pure radium chloride salt from several tons of pitchblende, an incredible feat at the time.

到 1902 年，居里夫妇从几吨沥青铀矿中提取了十分之克的纯氯化镭盐，这在当项了不起的壮举。

He tested a piece of pitchblende, the principal ore of uranium, and found it to be seven hundred million years old—very much older than the age most people were prepared to grant the earth.

他测试了块沥青铀矿, 发现它有七亿年的历史 - - 比大多数人准备给予地球的年龄要大得多。