Cerussite

Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruise to the mineral, whilst the present form, cerussite, is due to W. Haidinger (1845). Miners' names in early use were lead-spar and white-lead-ore.

Not to be confused with Sericite.
Cerussite
General
CategoryCarbonate mineral
Formula
(repeating unit)		Lead carbonate: PbCO3
Strunz classification5.AB.15
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma [62]
Identification
ColorColorless, white, gray, blue, or green
Crystal habitMassive granular, reticulate, tabular to equant crystals
TwinningSimple or cyclic contact twins
CleavageGood [110] and [021]
FractureBrittle conchoidal
Mohs scale hardness3 to 3.5
LusterAdamantine, vitreous, resinous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity6.53–6.57
Optical propertiesBiaxial (-)
Refractive indexnα = 1.803, nβ = 2.074, nγ = 2.076
Birefringenceδ = 0.273
Other characteristicsMay fluoresce yellow under LW UV
References[1][2][3]

Cerussite crystallizes in the orthorhombic system and is isomorphous with aragonite. Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form. Three crystals are usually twinned together on two faces of the prism, producing six-rayed stellate groups with the individual crystals intercrossing at angles of nearly 60°. Crystals are of frequent occurrence and they usually have very bright and smooth faces. The mineral also occurs in compact granular masses, and sometimes in fibrous forms. The mineral is usually colorless or white, sometimes grey or greenish in tint and varies from transparent to translucent with an adamantine lustre. It is very brittle, and has a conchoidal fracture. It has a Mohs hardness of 3 to 3.75 and a specific gravity of 6.5. A variety containing 7% of zinc carbonate, replacing lead carbonate, is known as iglesiasite, from Iglesias in Sardinia, where it is found.

The mineral may be readily recognized by its characteristic twinning, in conjunction with the adamantine lustre and high specific gravity. It dissolves with effervescence in dilute nitric acid. A blowpipe test will cause it to fuse very readily, and gives indications for lead.

Finely crystallized specimens have been obtained from the Friedrichssegen mine in Lahnstein in Rhineland-Palatinate, Johanngeorgenstadt in Saxony, Stříbro in the Czech Republic, Phoenixville in Pennsylvania, Broken Hill in New South Wales, and several other localities. Delicate acicular crystals of considerable length were found long ago in the Pentire Glaze mine near St Minver in Cornwall. Cerussite is often found in considerable quantities, and has a lead content of up to 77.5%.[4]

Lead(II) carbonate is practically insoluble in neutral water (solubility product [Pb2+][CO32−] ≈ 1.5×10−13 at 25 °C), but will dissolve in dilute acids.

Commercial uses

"White lead" is the key ingredient in (now discontinued) lead paints. Ingestion of lead-based paint chips is the most common cause of lead poisoning in children.[5]

Both "white lead" and lead acetate have been used in cosmetics throughout history, though this practice has ceased in western countries.[6]

Cerussite images
  • Crystals of cerussite, a secondary lead ore
  • At 890 carats, the Light of the Desert (located at Toronto's Royal Ontario Museum) is the world's largest faceted cerussite.[7]
  • Colorless cerussite crystal that has been included by wisps of light green malachite
  • Fine example of reticulated growth

See also

References

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Cerussite". Encyclopædia Britannica. 5 (11th ed.). Cambridge University Press. p. 762.

  1. Mineralienatlas
  2. Cerussite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-10.
  3. Cerussite. Mindat. Retrieved on 2011-10-10.
  4. "Mineral Information Service" (PDF). California Division of Mines. November 1949. p. 2. Retrieved 4 June 2016.
  5. Lightening the Lead Load in Children as cited in Lead Poisoning in Children Archived September 25, 2006, at the Wayback Machine, and California Poison Control System: Lead Poisoning Archived 2007-01-14 at the Wayback Machine
  6. Gunn, Fenja. (1973). The Artificial Face: A History of Cosmetics. — as cited in Leisure Activities of an 18th Century Lady and Reading Our Lips: The History of Lipstick Regulation in Western Seats of Power Archived 2006-09-05 at the Wayback Machine
  7. "Iconic: Light of the Desert". 2009-11-26. Retrieved 2012-07-25.
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