Dictionary:

anglesite

  (ăng'glĭ-sīt')

A lead sulfate mineral, PbSO₄, occurring in colorless or tinted crystals and formed by the weathering of lead ore.

[After ANGLESEY.]

A mineral with the chemical composition PbSO₄. Anglesite occurs in white or gray, orthorhombic, tabular or prismatic crystals or compact masses. It is a common secondary mineral, usually formed by the oxidation of galena. Fracture is conchoidal and luster is adamantine. Hardness is 2.5–3 on Mohs scale and specific gravity is 6.38. The mineral does not occur in large enough quantity to be mined as an ore of lead, and is therefore of no particular commercial value. Fine exceptional crystals of anglesite have been found throughout the world.

Environment

Secondary (weathered) deposits of lead ore in generally siliceous formations.

Tabular to prismatic crystals, may be elongated in any of the axial directions. Also massive, fine grained, granular to very compact.

Colorless to white or grayish, or tinted with impurities (red or green); surface turns golden in bleach. Luster adamantine; hardness 2Ɛ-3; specific gravity 6.4; fracture conchoidal; cleavage basal and prismatic. Brittle; transparent to translucent; often fluorescent (yellow-orange).

Lead sulfate (73.6% PbO, 26.4% SO ₃ )

Fuses very easily, forming white enamel, which is briefly yellow while still very hot. With continued blowpiping in the reducing flame, it boils away in spurts and finally yields lead bead.

Easily recognized as a lead mineral by blowpipe reactions. Distinguished from cerussite and phosgenite by lack of effervescence in acids and its behavior on charcoal.

Anglesite forms during the alteration by weathering of lead sulfide. The best crystals appear to be associated with granular lead ores rather than ores with large well-formed galena crystals, perhaps because the permeable galena is more porous and more readily attacked, letting the anglesite crystals grow faster. Usually associated with other lead minerals such as phosgenite and cerussite, and with other oxidized-zone minerals such as malachite and azurite (which may have preempted the available carbon dioxide). Far rarer than cerussite.

Fine, transparent, well-developed isolated crystals an inch (2-3 cm) or so in size are found in small cavities in the granular galena of Monteponi, Sardinia. Large crystals have been found at Tsumeb, Namibia (with a secondary copper ore), and with galena and cerussite at Broken Hill, New South Wales, and at Coeur d'Alene, Idaho. Fine crystals were once found with wulfenite, pyromorphite, and cerussite at the old Wheatley Mine, Phoenixville, Pennsylvania. Small crystals are common in holes in altering solid galena accompanied by tiny yellow sulfur crystals. Sometimes massive and nondescript sulfate rims will be found forming concentric gray to black bands enclosing a nucleus of unaltered galena. Good pseudomorphs of anglesite after cubes of galena have been found in the Joplin (Missouri) District and Bingham, New Mexico. In an interesting Mexican occurrence, yellowish tabular anglesite crystals are embedded in sulfur. There are numerous other good occurrences, too many to list.

Wikisource has an original article from the 1911 Encyclopædia Britannica about:

Anglesite

Anglesite specimen in its orthorhombic crystalline form

Anglesite is a lead sulfate mineral, PbSO₄. It occurs as an oxidation product of primary lead sulfide ore, galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, and is isomorphous with barite and celestine. It has a high specific gravity of 6.3 due to its lead content, 74% by mass; its hardness is 3. Color is white, gray with pale yellow streaks. It may be dark gray if impure.

It was first recognized as a mineral species by Dr. Withering in 1783, who discovered it in the Parys copper-mine in Anglesey; the name anglesite, from this locality, was given by F. S. Beudant in 1832. The crystals from Anglesey, which were formerly found abundantly on a matrix of dull limonite, are small in size and simple in form, being usually bounded by four faces of a prism and four faces of a dome; they are brownish-yellow in colour owing to a stain of limonite. Crystals from some other localities, notably from Monteponi in Sardinia, are transparent and colourless, possessed of a brilliant adamantine lustre, and usually modified by numerous bright faces. The variety of combinations and habits presented by the crystals is very extensive, nearly two hundred distinct forms being figured by V. von Lang in his monograph of the species; without measurement of the angles the crystals are frequently difficult to decipher. There are distinct cleavages parallel to the faces of the prism (110) and the basal plane (001), but these are not so well developed as in the isomorphous minerals barite and celestite.

Anglesite from Arizona

Anglesite from Arizona

Anglesite is a mineral of secondary origin, having been formed by the oxidation of galena in the upper parts of mineral lodes where these have been affected by weathering processes. At Monteponi the crystals encrust cavities in glistening granular galena; and from Leadhills, in Scotland, pseudomorphs of anglesite after galena are known. At most localities it is found as isolated crystals in the lead-bearing lodes, but at some places, in Australia and Mexico, it occurs as large masses, and is then mined as an ore of lead.

References

• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

External links

• Case Studies in Environmental Medicine (CSEM): Lead Toxicity
• ToxFAQs™: Lead

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