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Encyclopedia Britannica - Main :: PYR-RAY |
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PYROMORPHITE , a mineral
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. 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 hemihedrism as apatite, with which mineral
rule
bright shade of green, yellow or brown, and the lustre is resinous. The hardness is 3 and the specific gravity 6.57.1. 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 5.96.5) and usually lighter in colour; they bear the names " polysphaerite " (because of the globular fotm),'` miesite " from Mies in Bohemia, " nussieritefrom Nu8sihre near Beaujeu, Rhone, France, and " cherokine" from Cherokee county in Georgia. 694 Pyromorphite has resulted from the alteration of galena in the oxidized portions of metalliferous veins, and is frequently met with in the upper levels of lead mines. Finely crystallized specimens have been found at Braubach and Ems in Nassau, Wheal Alfred in Cornwall
Scotland , Phoenixville in Pennsylvania
Hope
Cornwall
(L. J. S.) End of Article: PYROMORPHITE If you wish, you can link directly to this article.
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