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.
Lead phases detected in lead paint include synthetic hydrocerussite, crocoite, anglesite, phoenicochroite and possible plattnerite.
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.
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.
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.
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.
The most colorful specimen displayed was a brilliant and exceedingly delicate, almost foot-wide plate of crocoite from Dundas, Tasmania.
Unfortunately, much of what had been found in the past carried a stubborn coating of cream-colored gibbsite which detracted from the fiery orange-red crocoite and made specimens virtually valueless.