到目前为止，大部分方式还在依赖象铱那样不实用的稀有原料作为引发反应的催化剂。
Until now, most approaches relied on impractically scarce materials like iridium as a catalyst that triggers the reaction.
日本从中国购买稀有的金属向国内电子工业和汽车工业提供生产原料。
Japan buys much of its rare metal from China to feed its electronics and car industries.
山羊绒属于稀有的特种动物纤维，是一种较为珍贵的纺织原料。
Cashmere is a rare special animal fiber, a noble textile material.
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