The Guide to Rocks and Minerals

In focus: Cerussite

Chemical Composition: PbCO3
Group: Carbonate
Colour: Colorless, White, Gray, Blue, Green
Streak: white
Hardness: 3-3.5
Density: 6.4-6.6
Luster: Adamantine
Cleavage: Distinct x2
Acid sensitive: yes

Cerussite is a lead carbonate (PbCO₃), also sometime known as white lead. In fact it's the same thing. Cerussite comes from Latin cerussa , and that means white lead. Documents describing natural cerussite can be found as early the 16th century when Cerussite is mentioned, for example, by K Gesner in 1565, though in those days it was known as Cerussa native. Cerussite owes its present name to Wilhelm von Haidinger, an Austrian mineralogist, geologist and physicist. He described Cerussite in a series of mineralogy lectures published in 1845 under the title 'Handbuch der bestimmenden Mineralogie '.

Cerussite is an important lead ore and a common secondary mineral of lead. It is formed by a chemical reaction between carbonated water and the mineral galena. Although in its pure form Cerussite is colourless or white, thethis mineral may be also different shades from gray to black due to the presence of sulfides or manganese oxides. Pink, blue, and green cerussite is also known, and yellow chromian cerussite can be found at several localities. A very notable feature of Cerussite is its great sparkle and high lustre. This is due to the high content of lead, giving an effect somewhat similar to lead crystal, where added lead means added sparkle. Due to its high lead content, Cerussite also has a very high density, approximately 6 times that of water. Since most minerals average about 3 times the density of water, that means that Cerussite is approximately 2 times denser than most minerals.

Cerussite belongs to the Aragonite Group. This group is well known producing twinning crystals and Cerussite is no exception. Indeed ,twinning is common in Cerrusite and it is one of the features which make this mineral a very desirable collectors' item. 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^oC.

Cerussite can be found in manyparts of the world, the most notable being Murcia, Spain; Tsumeb, Namibia; Congo; Morocco; Australia; Germany and Arizona, USA. Namibian mines in particular produce the world's finest examples of Cerussite, which are very pure transparent gem specimens. One of these was a featured item of the first Tuscan Gem and Mineral Show in 1983.

Mineral uses

Lead ore
Was once a main ingredient of lead paints. The paints are now discontinued due to the high risk of lead poisoning especially among children
It has been used in the production of cosmetics throughout history, though once again, due to danger of high lead content, its use has been now discontinued in
western countries.
A desirable collectors' item

Identification

The best field indicators of Cerussite are high lustre, shine and high gravity combined with twining. The mineral dissolves in dilute nitric acid. Under a blowpipe Cerussite will fuse readily indicating its lead content.

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