opal

opal
/ˈəupl; `opl/ n
bluish-white or milky-white semi-precious stone, often used in jewellery, in which changes of colour are seen 蛋白石
    a bracelet made of opals 蛋白石手镯
    [attrib 作定语]
an opal ring 蛋白石戒指.

牛津英汉双解词典