Crocoite


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crocoite

[′kräk·ə‚wīt]
(mineralogy)
PbCrO4 A yellow to orange or hyacinth-red secondary mineral occurring as monoclinic, prismatic crystals; it is also massive granular. Also known as crocoisite; red lead ore.

Crocoite

 

a mineral of chemical composition Pb[CrO4] (69.06 percent PbO, 30.94 percent CrO3). It sometimes contains admixtures of silver and zinc. Crocoite crystallizes in the mono-clinic system, forming slender prismatic or acicular crystals of a bright orange-red color. It is brittle, with a mineralogical hardness of 2.5–3.0 and a density of 5,990–6,000 kg/m3. Crocoite is formed in the oxidized zone of polymetallic lead-zinc ore deposits occurring in ultrabasic rocks (chromium sources) or in their immediate vicinity. The best-known variety of crocoite is extracted from the Berezov deposit in the Urals; it forms crystal druses in beresovite fissures. Other crocoite deposits are located in Tasmania.

References in periodicals archive ?
Conservators had noticed that some paintings using crocoite have become discolored, but researchers hadn't pinned down the cause.
Examples of these are synthetic cerussite or lead carbonite ([PbCO.sub.3]), synthetic anglesite or lead sulfate ([PbSO.sub.4]) and synthetic crocoite or lead chromate ([PbCrO.sub.4]).
against a black background, is a kingly crocoite specimen; on the back cover we make the pictorial acquaintance of bismuthinite, cassiterite, fluorite and siderite from little-known Tasmanian places.
But more along our lines were dozens of giant, superlative crocoites from Tasmania put in by Olivier Szentessy, Saint-Jean de Tholome, and the current Adelaide mine proprietor, Adam Wright.
Of course, from the moment you embark on this course, your mind is dwelling on one thought, and one thought alone--those folks you will encounter at the airport with the badges and patches that say "Transportation Security Administration" or "TSA." And, in your darkest moments, perhaps you wonder what would happen if those friendly TSA folks accidentally gouged a hole smack in the middle of your prized crocoite. It has happened to people before, and it can happen again.
Cases on special Australian topics included several by the Western Australian Museum (niobium and tantalum minerals of Western Australia; minerals of Whim Creek; Australian gold nuggets and crystal specimens); Virginia Tech (Argyle diamonds and inclusions in same); Harvard (Australian gold); the Geological Survey of New South Wales and the Mineralogical Society of New South Wales (both showing assorted New South Wales minerals); Dehne McLaughlin and Paul Melville (minerals of the Northern Territory); and Adelaide Mining Company (a huge and dramatic case of crocoite from the Adelaide mine).
Kunz, "unusually strong in the rare and expensive minerals such as wulfenite, crocoite, matlockite, vanadinite, and all the metallic minerals." That same June Niven made a quick two-week collecting trip to Middleville, Herkimer County, New York, where he secured nearly 500 pounds of the famous "Herkimer diamond" quartz crystals, clusters and matrix specimens.
Crocoite has been identified as "yellow, waxy patches in microcrystalline intergrowths of dawsonite and "K-feldspar" which also contain pyrochlore, pseudorutile and siderite" (Sabina, 1979).
There were Cornish and Russian specimens aplenty: chalcophyllite, torbernite, liroconite crystals to 1 cm, chalcocite crystals to 2 cm, olivenite, copper, crocoite, cerussite, feldspar crystals, etc.
Durable specimens may resist careless handling, earthquakes and other hazards; it is well to keep this in mind when making your selections for a display collection, even though vulnerable specimens of crocoite, mesolite or others may be appealing.
The locality is a deserted old prospect called the Chapacase mine, in the Antofagasta region, where Terry gophered into a small hole to follow the mineralized milky quartz vein until he found small pockets containing druses of very bright red wulfenite crystals, with individuals to 5 mm; in general aspect the specimens resemble Russian crocoite. Thick-tabular and fat bipyramidal wulfenite crystals may exist on the same specimen, and although they are small they congregate thickly, mostly on thumbnail-sized pieces, although Terry's largest matrix plates reach about 14 cm across.
Pete Bancroft's case was loaded with great pieces, including the famous Alma rhodochrosite, a fine California gold, a big Brazilian rose quartz crystal cluster from the Sapucaia mine and a superb Australian crocoite, to name just a few.