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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

CUPRITE


CUPRITE (Cuprit—Cuprite— уприт) (Agricola, G. 1546; Haidinger, W. 1845). The name reflects its copper composition, from Lat. “cuprum”.

Composition & Properties. Oxide – Cu2O, cubic system. Hardness 3.5-4. Density 5.8-6.1. Metal luster to diamond one, dull one. Cleavage in one direction. Fragile. It is found in the form of isometric crystals, needle aggregates of chalkotrichite and grained masses. Color: red, brown-red to black. Non-transparent to half-transparent, extremely rare – transparent. The size of its crystals is usually not more than 3 cm., and at some deposits it reaches 15 cm. The biggest crystal, about 2 kg. in mass, is kept in a private collection in the U.S.A. There are inclusions of native copper in this stone – cuprocuprite. Cuprite can be replaced with malachite, forming a pseudomorph, which is especially beautiful after slight polishing – malachite cuprite. There are also cuprite pseudomorphs on native copper. Cuprite was found in the form of regular oriented inclusions in crystals of baryte.

Deposits. Cuprite is formed in the zone of oxidation of cooper deposits. In Russia, its findings are known at many cooper deposits. in the Urals – Mednorudnyiansky, Gumeshevskiy and Turinskiy mines; in the Altai – Zmeinogorskoye and others; in the Primorskiy Region – Dal’negorskoye. In Kazakhstan, cuprite crystals up to 3 cm. at the Zhezkazgan deposit were found, and also at the deposits Nikolaevskoye, Chokpak and others are known. In Uzbekistan, its crystals are typical for the Olmaliq (Almalyk) deposit; in Kyrgyzstan – Chok Tegrek, near Adrasman; in Azerbaijan – Kedabek; in Armenia –– Ankavan. In the north of Tadzhikistan, at the Kaptar Khana deposit, in the region of Adrasman, cuprite crystals up to 1 cm. are placed as dendrites of native copper. In other countries, findings of gem-quality cuprite crystals were described: in England, Cornwall – in the region of Liskeard; in France – crystals up to 8 cm. at the Chessy deposit, near Lyon, Rhône-Alpes. In Congo (Kinshasa), at the Mushamba mine, they found well-formed crystals of cuprite up to 3 cm. Similar cuprite is known in Congo (Brazzaville) at the Mindouli deposit, near Kaounga Renéville. In Namibia gem-quality cuprite at the Tsumeb was extracted; and ups to 14 cm. at Ongaja mine, near Windhuck. At the Emke mine, near Ongania, they were up to 15 cm. in cross-section and up to 2 kg. in mass; and at the Otavi deposit concretions of cuprite in clusters with malachite and chalcocite were found. In Australia, cuprite was extracted in Queensland, in the region of Mt. Isa; and in the south of the country – at the Burra Burra deposit, to the west from Burra and to the north from Adelaide. In the U.S.A., deposits of gem-quality cuprite are known in Arizona near Bisbee, Cochis Co. – Copper Queen mine and others, with crystals up to 3 cm.; and Morenci mine, Greenlee Co., from which they received faceted stones up to 6 ct. In New Mexico, similar cuprite was discovered at the deposits Santa Rita and Chino Pit., Grant Co. In Mexico, an ornamental variety of cuprite is characterized with numerous inclusions of azurite and malachite, and red or brown one has its own name – chrysocarmen, calmazul or burnit.

Synonyms. Red copper | Ruby copper | Chrysocolla cuprite | Black copper glass | Red copper glass | Red copper head | ~ Copper ore: brown ~, glassy ~, octahedral ~, plush ~, red ~, red glassy ~ | Ruberite | Copper ruby.

Treatment. Half-transparent crystals of cuprite are faceted, non-transparent ones are cut in silvery cabochons. They are well polished, but under oxidation they receive rose tone. Very beautiful are cabochons of red cuprite with inclusions of blue azurite and green malachite. The biggest volume of faceted stones reached 300 ct. In the AMNH, N,Y., there is a faceted cuprite 172 ct., and in the Smiths. Inst., Wash. – 182 and 203.75 ct. Sometimes they process massive fine grained aggregates of brick copper ore, and in mixture with limonite – liver copper ore. In the U.S.A., in Pennsylvania, the term “cuprite” is used also for ornamental epidote rhyolite with inclusions of cuprite.

Similarity. Cuprite looks like hematite, cinnabar, pyrargyrite and proustite; from which it differs with its physical properties and its reaction on Cu. Glassy variety of cuprite – copper glass looks like obsidian.

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