Crocoite is a mineral consisting of lead chromate and crystallizing in a monoclinic crystalsystem, and it is the only chromate of any importance found in nature.
In the study of optical properties of low class crystalsystem, the identification of optic sign has important meaning to unknown crystal and mineral determination.
在低级晶族光学特性的研究中，光性符号的确定对未知晶体及矿物的鉴定有着重要的意义。
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This article tries to feel about the method and graft parameter of preparing petroleum naphthalene by the experiment of the branch crystalsystem to make tar naphthalene.