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Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

CERUSSITE


CERUSSITE (Cerussit—Cérusite—÷еруссит) (Gesner, 1545 in Haidinger, W. 1845), from Lat. “cerussa” – white lead, ancient term for artificial lead carbonate.

Composition & Properties. Carbonate – Pb[CO3], orthorhombic system. Hardness 3-3.5. Density 6.5. Greasy luster to diamond one. Cleavage in two directions. Fragile. Cerussite is found in the shape of lamellar, more rarely columnar crystals, which often form pseudohexagonal trillings up to 20 cm., sometimes, clustered into voluminous lattice aggregates. Pure crystals are colorless, turbid ones are milky-white. Transparent to half-transparent. Color depends on admixtures: dark gray to black one – on inclusions of manganese sulfides and oxides, brownish one – on iron oxides, blue one – on copper minerals, sometimes there is admixture of zinc. Inclusions in cerussite lead to the effect of cat’s-eye in cabochons. Lead mica is a lamellar variety of cerussite and white lead ore is represented in massive aggregates of grained cerussite. Together with cerussite, in the zone of oxidation of ore veins, they find hydrocerussite in the shape of colorless fine-lamellar crystals. They are used in imitations of pearls as artificial film coverings. Diffraction and interference of light from micro-crystals of hydrocerussite on the surface of “pearls” beads produce the effect of chatoyancy.

Deposits. Cerussite is formed in the zone of oxidation of ore deposits, where it is developing on galena and anglesite. In Russia, gem-quality crystals of cerussite were known in Transbaikalia: at the Kadainskiy and Smirnovskiy mines, near Nerchinskiy Zavod, as well as at the Trekhsvyatitel’skiy mine, near Gorny Zerentui; at the Taininskiy and Gazimurskiy mines, near Gazimurovskiy Zavod. In the Fersman’s Museum, Moscow, there is a sample of cerussite from Transbaikalia, 10 cm.. long. In Kazakhstan, crystals and druses of cerussite are found in the Rudnyi Altai, at the Zyryanovskiy and Leninogorskiy mines; in Central Kazakhstan – at the deposits Ak-Dzhal, Zhayrem and Kyzylespe; also trilligs up to 10 cm at the Ushkatyn-III deposit are find. In the South Kazakhstan, at the Ashchysay (form. Achi-Sai) deposit, the Karatau Mts., colorless crystals were discovered. In North Tadzhikistan, significant volumes of cerussite occur in crystals up to 2 cm.; at the Kansay deposit, Karamazar, Khujand Dist., it was extracted.

In Europe, we should mention the following countries, where large, gem-quality crystals were extracted: in Bulgaria – at the deposits Madjarovo and Madan; in Czech Rep. – in crystal up to 5 cm. at Sribro (form. Miss) and in Príbram; in Great Britain – in the Scotland, Leadhills area; in Italy – in Sardinia Is. In the south of Poland, near Kraków, there are several deposits of cerussite in a sedimentary layer of dolomites. In Africa, cerussite in crystals up to 8 cm. long in the north of Morocco, at the Touissit deposit, near Udjd, was discovered; also at the Mibladen mine, near Midelt. In Namibia, excellent collection material at the Tsumeb deposit in the shape of lattice clusters of cerussite crystals up to 60 cm., were extracted. From the same place the best gem-quality rough material comes, which displays the effect of cat’s-eye after cut. In Congo (Brazzaville), cerussite in crystal up to 18x15 cm. at the M’Fouati deposit and at Mindouli is known; also in Zambia – at the Kabwe (form. Broken Hill) deposit, where its light blue crystals are found.

In Australia, gem-quality crystals of cerussite are extracted as additional material at Broken Hill the lead-zinc deposit, New South Wales. Usually, they are represented with twin-crystal clusters in the shape of lattice aggregates up to 33x26 cm. in size. In the Tasmania Is., they find canary-yellow cerussite at the Comet mine, near Dundas. On the New Caledonia Is., France, cerussite was discovered at the Meretris mine. In the U.S.A., in Arizona, at the Mammoth deposit, they found cerussite cat’s-eye; and at the Bisbee mine, Grand Reef mine and Tombstone they discovered crystals of cerussite available for processing. In the states Utah and Colorado, at cerussite deposits, they found lattice clusters of its crystals up to 5 cm. In Brazil, in the São Paolo State, large crystals of cerussite were found at the Santana Nova deposit, near Lajerdo.

Synonyms. Acrusite | Bleispath, Germ. | Bleiweiß, Germ. | Horn lead | Black lead ore | Horn lead ore | White lead ore | ~ spar: blue~ , lead ~, black lead ~, white lead ~, zinc lead ~.

Treatment. Transparent, colorless, pale yellow and brown crystals of cerussite are faceted sometimes. They display high level of dispersion, diamond luster, but because of low hardness cerussite is classified as a collection gemstone. In the Smiths. Inst., Wash., there is a pale yellow faceted gem from the Tsumeb deposit, Namibia, in 4.7 ct. From the same deposit the biggest faceted gemstone was received – 898 car; it is kept in the Royal Ontario Museum. From that place and from Arizona, the U.S.A., rough material for cabochons comes with the effect of cat’s-eye and the weight up to 6 ct. In faceted form cerussite looks like diamond and sphalerite.

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