Revision 1180225 of "Pyromorphite" on enwiki

'''Pyromorphite''' is a [[mineral]] species composed of [[lead]] chlorophosphate (PbCl)Pb<sub>4</sub>(P04)<sub>3</sub>, sometimes occurring in sufficient abundance to be mined as an [[ore]] of lead. [[Crystal]]s are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. As proved by the etched figures on the faces, crystals possess the same parallel-faced hemihecirism as [[apatite]], with which mineral [[pyromorphite]] and also [[mimetite]] are isomorphous. Between pyromorphite and the corresponding chloro-arsenate (mimetite), the resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests.

They were formerly confused under the names green lead ore and brown lead ore (German, Grünbleierz and Braunbleierz). The phosphate was first distinguished chemically by M. H. Kiaproth in 1784, and it was named pyromorphite by J. F. L. Hausmann in 1813.

The color of the mineral is usually some bright shade of green, yellow or brown, and the [[luster]] is resinous. The hardness is 3, and the [[specific gravity]] 6.5 - 7.1. Owing to isomorphous replacement of the [[phosphorus]] by [[arsenic]] there may be a gradual passage from pyromorphite to mimetite. Varieties containing [[calcium]] isomorphously replacing lead are lower in density (specific gravity 5.9 - 6.5) and usually lighter in color; they bear the names polysphaerite (because of the globular form), miesite from [[Mies]] in [[Bohemia]], nussierite from [[Nussihre]] near [[Beaujeu]], [[Rhfine]], [[France]], and cherokine from [[Cherokee County, Georgia|Cherokee County]] in [[State of Georgia|Georgia]].

== See also ==
* [[List of minerals]]

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[[Category:Minerals]]