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Pb
Cubic
Lead was first reported from Franklin by Foote (1898), and the extant sparse information on it was summarized by Palache (1935) and Frondel (1972). It was noted at Franklin associated with copper, domeykite, and cuprostibite by Burke and Dunn (1988), but it has not been reported from Sterling Hill.
Lead from Franklin is gray, soft, and sectile. Isolated microscopic platelets or films within willemite and other transparent minerals commonly have a silvery appearance. It also occurs as masses up to 4 g. There have been no chemical studies other than the observation by Burke and Dunn (1988) that their material (within willemite) has over 99.5 wt. % Pb.
Foote (1898) reported lead as fine scales associated with roeblingite, hancockite, and other species. In general, most Franklin lead likely occurs as finely-disseminated, microscopic platelets in minerals which do not accommodate solid solution of Pb. In replacement assemblages, it appears as gray, diffuse, impure concentrations, commonly parallel to reaction surfaces. Verified specimens are rare, but the occurrences were sufficiently numerous that a great many unstudied specimens exist.
The majority of specimens are from assemblages found near the Parker and Palmer Shafts. Here, lead is commonly associated with feldspars, willemite, minehillite, margarosanite, and andradite, together with less commonly associated minerals, such as rhodonite, bustamite, micas, and numerous silicates. Like copper, lead may be much more widespread at Franklin than is known. It is common as platelets in willemite, but such specimens have an undesirable appearance and thus may have been casually collected if at all. Megascopically recognizable material has been selectively retained. If lead is dispersed through the orebody as inclusions in primary, high-temperature minerals, it might have been the source of some of the secondary Pb minerals, such as pyrobelonite, hedyphane, or descloizite, which occur in vein assemblages. This matter remains uninvestigated.
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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Link
to homepage
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This
page created: January 11, 2001 |
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