Anglesite

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Anglesite
Anglésite, galène, soufre 300-4-5394.JPG
Anglesite from Morocco
General
CategorySulfate minerals
Formula
(repeating unit)
PbSO4
Strunz classification7.AD.35
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Identification
ColorColorless to white, commonly tinted gray; orange, yellow, green, blue, rarely violet
Crystal habitGranular, banded, nodular to stalactitic
Cleavage[001] good, [210] distinct
FractureBrittle to conchoidal
Mohs scale hardness2.5–3.0
LusterAdamantine crystals, dull when massive earthy
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity6.3
Optical propertiesBiaxial (+)
Refractive indexnα = 1.878
nβ = 1.883
nγ = 1.895
Fusibility1.5
References[1][2][3]

Anglesite is a lead sulfate mineral with the chemical formula 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 contains 74% of lead by mass and therefore has a high specific gravity of 6.3. Anglesite's color is white or gray with pale yellow streaks. It may be dark gray if impure.

It was first recognized as a mineral species by William 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 [it] 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.[4]

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.[4]

Anglesite is sometimes used as a gemstone.[5]

Gallery[edit]

See also[edit]

Lead(II) sulfate

References[edit]

  1. ^ "Anglesite" (PDF). Handbook of Mineralogy. Rruff.geo.arizona.edu.
  2. ^ "Anglesite Mineral Data". Webmineral.com. Retrieved 2014-05-15.
  3. ^ "Anglesite: Anglesite mineral information and data". Mindat.org. Retrieved 2014-05-15.
  4. ^ a b  One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Anglesite" . Encyclopædia Britannica. 2 (11th ed.). Cambridge University Press. p. 10.
  5. ^ Oldershaw, Cally (2003). Firefly guide to gems. Toronto, Ont. Buffalo, N.Y: Firefly Books. p. 84. ISBN 978-1-55297-814-6.

External links[edit]