Earth Metals,Rare

《英文msh詞典》Earth Metals,Rare
[入口詞] Earth Metals,Rare
[主題詞] Metals,Rare Earth
[英文釋義] A group of elements that include SCANDIUM,YTTRIUM; and the LANTHANOID SERIES ELEMENTS. Historically,the rare earth metals got their name from the fact that they were never found in their pure elemental form,but as an oxide. In addition they were very difficult to purify. They are not truly rare and comprise about 25% of the metals in the earth's crust.