Pyromorphite
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Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5(PO4)3Cl, sometimes occurring in sufficient abundance to be mined as an ore of lead.<ref>Template:Cite book</ref> Crystals are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid.<ref>Template:Cite book</ref> Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found.<ref name="pa88">Template:Cite book</ref> Pyromorphite is part of the apatite group of minerals and bears a close resemblance physically and chemically with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl).<ref>Template:Cite book</ref> 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).Template:Cn
The phosphate was first distinguished chemically by M. H. Klaproth in 1784,<ref>Template:Cite book</ref><ref>Details of Klaproth's chemical analysis of pyromorphite appear in: Klaproth (1785) "Ueber die Phosphorsäure im Zschopauer grünen Bleyspathe" (On phosphoric acid in green lead spar from Zschopau), Beyträge zu den chemischen Annalen, 1 (1) : 13–21.</ref><ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and it was named pyromorphite by J. F. L. Hausmann in 1813.<ref>Template:Cite book</ref><ref>Template:Cite book</ref> The name is derived from the Greek for pyr (fire) and morfe (form) due to its crystallization behavior after being melted.<ref name=Webmin/>
Paecilomyces javanicus is a mold collected from a lead-polluted soil that is able to form biominerals of pyromorphite.<ref>Template:Cite journal</ref>
Properties and isomorphismEdit
The color of the mineral is usually some bright shade of green, yellow or brown, and the luster is resinous. The hardness is 3.5 to 4, and the specific gravity between 6.5 and 7.1.<ref name="pa88"/> 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 Stříbro (pronounced Mies in German) in Bohemia, nussierite from Nuizière, Chénelette, near Beaujeu, Rhône, France, and cherokine from Cherokee County in Georgia.Template:Citation needed
GalleryEdit
- Pyromorphite-137773.jpg
A pocket of crystals of pyromorphite from China
- Pyromorphite-157594.jpg
Miniature of sharp, lustrous, apple green color crystal "sprays" on matrix
- Pyromorphite-137954.jpg
Fine crystals of pyromorphite from Daoping Mine, Guangxi Zhuang Autonomous Region, China
- Pyromorphite-118273.jpg
Green pyromorphite crystals densely carpet the display side of the large matrix
- Pyromorphite-Cerussite-Caledonite-278353.jpg
Green pyromorphite microcrystals cover the vuggy, quartz-rich matrix. Seams of tiny cerussite crystals and crusts of contrasting, powder-blue caledonite round out this very rich lead ore specimen from an old Leadhills mine.
See alsoEdit
ReferencesEdit
External linksEdit
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