Cerussite out of the oxidation zone - Locality: Tsumeb, Southwest-Africa (*)
Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and an important ore of lead. The name is from the Latin cerussa, white lead. Basic lead carbonate was first prepared by the Arabian alchemist, Jabir ibn Hayyan (Geber), in the 8th century. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruse 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.
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.
Lead(II) carbonate is practically insoluble in neutral water (solubility product [Pb2+][CO32-] ≈ 1.5x10-13 at 25 °C), but will dissolve in dilute acids.
"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.
Both "white lead" and lead acetate have been used in cosmetics throughout history, though this practice has ceased in Western countries.
* Venetian Ceruse - Cerussite based cosmetic worn by Elizabeth I of England.
1. ^ http://rruff.geo.arizona.edu/doclib/hom/cerussite.pdf Handbook of Mineralogy
* Mineral galleries