Harmotome n. : A hydrous silicate of alumina and baryta, occurring usually in white cruciform crystals; cross-stone.

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Taxonomy
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Defination from the web:
Harmotome is a mineral, one of the rarer zeolites; a hydrated barium silicate with formula: (Ba 0.5,Ca 0.5,Na,K)5Al 5,Si 11O 32·12(H2O). It forms vitreous white well defined monoclinic crystals, often associated with calcite ... Retrieved from "http://en.wikipedia.org/wiki/Harmotome" ...