Powellite


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powellite

[‚pau̇·ə‚līt]
(mineralogy)
Ca(WMo)O4 A commercially important tungsten mineral, crystallizing in the tetragonal system; isomorphous with scheelite (CaWO4).

Powellite

 

(named after the American geologist J. Powell), a mineral, calcium molybdate (CaMoO4). Powellite contains 28.48 percent CaO and 71.52 percent M0O3; some varieties contain up to 10.3 percent WO3. The mineral crystallizes in the tetragonal system. Sometimes it is found in the form of small crystals of a lamellar or dipyramidal habit. Most often it forms cryptocrystalline aggregates—products of alteration of molybdenite—which sometimes preserve the foliated structure typical of molybdenite. Its color ranges from white to dark green and brown. Powellite has a hardness of 3.5 on Mohs’ scale and a density of 4,250–4,520kg/m3. In ultraviolet light a yellow luminescence is usually detected. Powellite is a characteristic mineral of the oxidized zone of the ores of molybdenum deposits.

References in periodicals archive ?
The powellite phase which appears in a high proportion for samples calcined between 500 and 800[degrees]C, it is few active for the hydrotreating reactions.
On the basis of Powellite doctrine we should welcome today's immigrants, since they dilute even further the non-white presence here.
As an old Powellite right-wing Conservative, it gave me little pleasure to oppose the official Welsh Conservative candidate.
His comments fit the Powellite agenda perfectly - casual references to foreigners, almost as if they are a sub-species, the mythology of immigration, the clear insinuation that a further influx of immigrants to this country must be a bad thing because immigrants are a bad thing.
These include arseniosiderite, bromargyrite, cabalzarite, chalcophyllite, clinoclase, clinotyrolite, cobaltkoritnigite, cornubite, fornacite, geminite, litharge, mottramite, nickellotharmeyerite, novacekite, parnauite, powellite, uvarovite, walentaite, wulfenite, yukonite and zalesiite.
Of these, Ernesto felt fairly confident in naming scorodite, powellite, lotharmeyerite, and zincroselite, and he suspected that lavendulan, chalcophyllite and sainfeldite were present as well.
Accessory minerals are biotite, calcite, cassiterite, chalcopyrite, chlorite, ferberite, goethite, titanite, zircon, bismuth, powellite, scheelite and minor sulfides such as arsenopyrite, pyrite and molybdenite (Schlogl, 1984).
It is in fact a return to the Powellite anti-immigration agenda.
If he does so in future, I hope he brings more of the new crystals of powellite which he had in France; these were found, he says, in early 2006 in a well-digging at Jamner, near Jalgaon, in India's zeolite-bearing Deccan Plateau.
However, she was attacked as a 'Powellite' and as a 'racialist' by black leaders and by white liberals.
They flagged me down and showed me several fine new specimens of powellite, one having a mirror-bright, doubly terminated powellite crystal 2.5 cm across on a spray of scolecite measuring about 1.25 X 10 cm.
Among them were Lord Biffen, with whom there had sometimes been political differences, and Mr Nicholas Budgen, who had often been outspoken in his support of Powellite immigration theory, and his former Unionist Party leader in Northern Ireland, Mr JamesMolyneux.