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www.mineralgallery.co.za Minerals A-E |
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Cerussite |
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Name
Cerussite
Chemistry
PbCO3, Lead Carbonate
Uses
As a specimen and as an ore of lead.
Color
Generally colorless or with light shades of yellow or gray.
Hardness
3-3.5
Specific gravity
6.5 very heavy for a translucent mineral
Crystals
It belongs to the orthorhombic group and forms prismatic or tabular parallel to a side pinacoid. It also forms bipyrimidal or pseudo-hexagonal star-like twins.
Accompanied by:
Anglesite, galena, smithsonite, pyromorphite and sphaelerite.
Fracture
Conchoidal
Luster
Adamantine
Cleavage
Prismatic in two directions with a distinct cleavage.
Streak
White
Similar to:
Anglesite
Cerussite is a carbonate mineral.
It is a widely distributed and common ore of lead. It is formed by the action of carbonated solutions on galena in the upper, oxidized zones of lead veins. Cerussite forms white or tinted tabular, pyramidal, or prismatic crystals (orthorhombic system) and crystal aggregates, as well as compact or granular masses. Luster is adamantine to vitreous.
Cerussite is a popular collection mineral. It can form some geometrically intricate structures and spoked star shapes because of multiple twinning. Twinning is common in Cerussite and besides the intricate structures mentioned already, singular twins are also interesting and a must for collectors who are fond of twinned crystals.
Cerussite is a minor ore of lead. It has a very high luster due to the lead content. Just as leaded crystal glass sparkles more brilliantly because of its lead content, so too does Cerussite.
The specimens from Tsumeb is much sought after.
Cerussite specimens from Tsumeb vary greatly in form and color and associations. Beside azurite it is probably the most famous mineral from this locality. The first oxidation zone, the finest examples occurred between 150 and 250 meters. As with anglesite no more crystals have been found deeper than 400 meters below surface in the first oxidation zone, but again in the other zones. The largest crystals were about 60 cm in length. Isometric crystals measure up to fist size.
The color of cerussite ranges from
Colorless, yellow, green, brown, red to black The black crystals are filled with inclusions of galena.
A green color is is due to inclusions of malachite.
Gray is formed by Galena inclusions.
Red have inclusions of cerussite.
The finest Cerussite are the colorless sharp edged ones found at Tsumeb.
The cerussite crystals from Tsumeb are unquestionably the largest and finest found anywhere in the world. Superb, clear, twinned crystals have been found up to 60 cm (2 feet) in length. Most crystals are twinned but a few untwinned specimens are occasionally seen. Cerussite is the most abundant secondary lead mineral at Tsumeb.
Twinned groups may form six-pointed 'stars' similar in appearance to snow flakes (but much larger!) or they may form large, reticulated groups and masses of complex shape. Some crystals are thick, water-clear and highly dispersive with many crystal modifications; others are bladed to elongated and milky.
Many of the spectacular large and beautiful cerussite crystals were found singly in solution cavities in the ore or in gangue. Mineral assemblages rich in cerussite are very numerous. In the samples I investigated, cerussite occurred with a total of 29 other secondary minerals. In order of their occurrence, the most important are duftite, smithsonite, malachite, mimetite, willemite and azurite. Cerussite is relatively rare in assemblages including numerous other minerals such as mottramite, wulfenite, adamite and olivinite. The indications are that these minerals are not stable near cerussite or perhaps they have fundamentally different conditions of formation.
One of the most common assemblages at Tsumeb includes cerussite and duftite. Cerussite is usually younger than the duftite on these specimens. Occasionally one observes two generations of duftite. Specimens also occur in which the older duftite generation is missing or in which duftite and cerussite appear to have crystallized simultaneously. Often a fine coating of goethite needles is the earliest mineral to form on these specimens and a white pearly coating of dolomite crystals to 5 mm is the most recent.
