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CuSiO2(OH)2 A rare emerald-green mineral that forms hexagonal, hydrous crystals.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a mineral whose structural features correspond to the so-called cyclosilicate type. Its chemical composition is Cu6[Si6O18] 6H2O. Dioptase crystallizes in the trigonal system, forming acicular short-columnar small crystals, and accumulates in druses or granular aggregates of bright emerald green color. It is transparent and has an intense luster. The mineral has a hardness of 5.0-5.5 on the mineralogical scale and a density of 3,280-3,350 kg/m3. It is usually found in the oxidized zones of copper sulfide deposits along with malachite, calcite, and quartz and sometimes with hemimorphite and other minerals. Dioptase was discovered by Ashir Muhammad of Bukhara in 1785 (deposit at Altyn-Tiube in Central Kazakhstan). There are also a number of deposits in Africa (Katanga and elsewhere).

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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The dioptase crystals in Nkanga's performance, and the image on the backdrop, come from a mine she visited in Namibia which is known for its rare minerals.
Two hundred dollars (or just a bit more) would have bought from Stefan Stolte a fine small-miniature-size matrix specimen of dioptase from the Omaue mine, Namibia, with a sharp, complete dioptase crystal to around 2 cm.
Marty drove the crates to Julie's house at 3 a.m., and after opening them the next day and covering a pool table with sparkling dioptase, the Zweibels were officially hooked on Tsumeb.
Some of the dioptase crystals mentioned above may be coated with a little malachite or calcite and not be very shiny.
Ladislav Turecky), Dioptase, Malachite and Shattuckite from Namibia (Paul and Antoine Weghorn), and Minerals of Turkey (Christa Zechner).
The locality is well-known for fine examples of common secondary minerals such as cerussite, dioptase and wulfenite, and also for rarer species such as diaboleite, caledonite, bideauxite and leadhillite which represent some of the finest known examples of their species.
The Kosnars of Mineral Classics had about 15 specimens of seriously flashy dioptase from a find made early last December in the Kimbedi mine, Republic of the Congo (ROC)--also called Congo-Brazzaville.
He moved on to French Equatorial Africa where he mined dioptase, then northern Rhodesia, Madagascar, Mozambique, Namibia, Kenya and South Africa.
Fine examples of cerussite, dioptase, malachite, azurite, wulfenite, smithsonite and vanadinite have been collected there, as well as some of the finest known examples of a number of rarer species such as boleite, diaboleite, caledonite, hydrocerussite, linarite, matlockite and leadhillite.
Dioptase from Tsumeb is the standard against which all other dioptase specimens are measured.
Other fabulous specimens include Arizona petrified wood, dioptase from Africa, native gold specimens from Idaho Falls, Colorado, long acicular crystals of millerite [with] arsenopyrite from Mexico, and jamesonites from Mexico.
Other exhibits included a case showing early mining methods, a case of antique mine lamps, worldwide uranium and rare earth ores, gold specimens, fluorescent minerals, malachite pseudomorphs, Richard Bideaux's case of dioptase, wulfenite, cerussite and descloizite, numerous cases of "rare and beautiful thumbnails," and so on.