And in rare cases, petrified wood, shells, teeth, and even bones of extinct organisms are made of opal.

在极少数情况下，木变石、贝壳、牙齿甚至是灭绝生物的骨骼都形成了欧泊。

Though a goodly number of animals have now been identified as dating from it, many bore scant resemblance to those which followed and, in particular, precious few had easily preserved hard parts in the form of shells, teeth or bones.

虽然现在已经确定有相当多的动物可以追溯到它，但许多动物与后来的动物几乎没有相似之处， 尤其是很少有珍贵的动物可以轻易地保存为贝壳、牙齿或骨头等坚硬的部分。