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Powellite

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John Wesley Powell, second Director of the USGS. Served from 1881-1894. Profile early in his term of office as Director
Formula:
Ca(MoO4)
Colour:
Yellow, straw-yellow, yellow-brown, brown, greenish yellow, grey, blue or black, colourless; black material is deep blue in transmitted light.
Lustre:
Sub-Adamantine, Resinous, Pearly
Hardness:
3½ - 4
Specific Gravity:
4.26
Crystal System:
Tetragonal
Member of:
Name:
Named in 1891 by William Harlow Melville in honor of the American geologist and explorer, John Wesley Powell [March 24, 1834 Mount Morris, New York. USA – September 23, 1902 North haven, Maine, USA], second Director of the U.S. Geological Survey.
Isostructural with:
Powellite-Scheelite Series.

An uncommon secondary mineral, typically formed in the oxidation zones of molybdenum-bearing hydrothermal deposits, rarely in basalt cavities, tactites, and granite pegmatites.

Visit gemdat.org for gemological information about Powellite.


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Classification of PowelliteHide

Approved, 'Grandfathered' (first described prior to 1959)
7.GA.05

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
G : Molybdates, Wolframates and Niobates
A : Without additional anions or H2O
Dana 7th ed.:
48.1.2.2
48.1.2.2

48 : ANHYDROUS MOLYBDATES AND TUNGSTATES
1 : AXO4
27.3.2

27 : Sulphites, Chromates, Molybdates and Tungstates
3 : Molybdates

Pronounciation of PowelliteHide

Pronounciation:
PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of PowelliteHide

Sub-Adamantine, Resinous, Pearly
Transparency:
Transparent, Translucent
Comment:
Lustre sub-adamantine on crystal faces; greasy on fracture surfaces. Pearly lustre manifests on foliated pseudmorphous material.
Colour:
Yellow, straw-yellow, yellow-brown, brown, greenish yellow, grey, blue or black, colourless; black material is deep blue in transmitted light.
Comment:
May exhibit zoned colouration.
Hardness:
3½ - 4 on Mohs scale
Cleavage:
Poor/Indistinct
Indistinct on {112} {011} and {001}.
Fracture:
Irregular/Uneven
Density:
4.26 g/cm3 (Measured)    4.255 g/cm3 (Calculated)

Optical Data of PowelliteHide

Type:
Uniaxial (+)
RI values:
nω = 1.974 nε = 1.984
Max Birefringence:
δ = 0.010
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
Pleochroism:
Visible
Comments:
In deeply colored specimens (Houghton County, Michigan, USA):
O = Blue
E = Green

Chemical Properties of PowelliteHide

Formula:
Ca(MoO4)
IMA Formula:
CaMoO4
Common Impurities:
W

Crystallography of PowelliteHide

Crystal System:
Tetragonal
Class (H-M):
4/m - Dipyramidal
Space Group:
I41/a
Cell Parameters:
a = 5.222(1) Å, c = 11.425(3) Å
Ratio:
a:c = 1 : 2.188
Unit Cell V:
312.92 ų
Z:
4
Morphology:
Crystals dipyramidal {111}, with {011} and {112}; less commonly flat tabular to paper-thin on {001}, exhibiting many minor forms. Form e sometimes striated parallel to the intersection with vertical plane {110}; diagonal striations parallel to {131} observed on e and W. Tetragonal-dipyramidal symmetry evident only in the zones of [111]. Forms crusts; pulverulent; ocherous; massive.
Comment:
On synthetic material

X-Ray Powder DiffractionHide

Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Type Occurrence of PowelliteHide

Place of Conservation of Type Material:
U.S. National Museum of Natural History, Washington, D.C., USA: #80674.

Other Language Names for PowelliteHide

Catalan:Powellita
Dutch:Powelliet
German:Powellit
Italian:Powellite
Spanish:Powellita

Relationship of Powellite to other SpeciesHide

Member of:
Other Members of this group:
RaspitePb(WO4)Mon. 2/m : P21/b
ScheeliteCa(WO4)Tet. 4/m : I41/a
StolzitePb(WO4)Tet. 4/m : I41/a
WulfenitePb(MoO4)Tet. 4/m : I41/a
Forms a series with:

Common AssociatesHide

Apophyllite
LaumontiteCaAl2Si4O12 · 4H2O
MolybdeniteMoS2
MolybdeniteMoS2
StilbiteThis name now refers to the minerals Stilbite-Ca and Stilbite-Na.
Associated Minerals Based on Photo Data:
Stilbite56 photos of Powellite associated with Stilbite on mindat.org.
Scolecite41 photos of Powellite associated with Scolecite on mindat.org.
Fluorapophyllite-(K)36 photos of Powellite associated with Fluorapophyllite-(K) on mindat.org.
Szenicsite23 photos of Powellite associated with Szenicsite on mindat.org.
Stilbite-Ca21 photos of Powellite associated with Stilbite-Ca on mindat.org.
Molybdenite20 photos of Powellite associated with Molybdenite on mindat.org.
Quartz19 photos of Powellite associated with Quartz on mindat.org.
Apophyllite18 photos of Powellite associated with Apophyllite on mindat.org.
Brochantite11 photos of Powellite associated with Brochantite on mindat.org.
Calcite8 photos of Powellite associated with Calcite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

7.GA.05Fergusonite-(Ce)(Ce,La,Nd)NbO4
7.GA.05Fergusonite-(Nd)(Nd,Ce)(Nb,Ti)O4
7.GA.05Fergusonite-(Y)YNbO4Tet. 4/m : I41/a
7.GA.05ScheeliteCa(WO4)Tet. 4/m : I41/a
7.GA.05StolzitePb(WO4)Tet. 4/m : I41/a
7.GA.05WulfenitePb(MoO4)Tet. 4/m : I41/a
7.GA.10Formanite-(Y)YTaO4Tet. 4/m : I41/a
7.GA.10Iwashiroite-(Y)Y(Ta,Nb)O4Mon. 2/m : P2/b
7.GA.15Paraniite-(Y)Ca2Y(AsO4)(WO4)2Tet. 4/m : I41/a

Related Minerals - Dana Grouping (8th Ed.)Hide

48.1.2.1ScheeliteCa(WO4)Tet. 4/m : I41/a

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

27.3.1LindgreniteCu3(MoO4)2(OH)2Mon. 2/m : P21/m
27.3.3WulfenitePb(MoO4)Tet. 4/m : I41/a
27.3.4KoechliniteBi2MoO6Orth. mm2 : Pna21
27.3.5SedoviteU(MoO4)2Orth.
27.3.6MouriteUMo5O12(OH)10Mon.
27.3.7Iriginite(UO2)Mo2O7 · 3H2OOrth. mmm (2/m 2/m 2/m) : Pbcm
27.3.8Umohoite(UO2)MoO4 · 2H2OTric.
27.3.9MoluraniteH4U4+(UO2)3(MoO4)7 · 18H2O
27.3.10CousiniteMgU2Mo2O11 · 6H2O
27.3.11Calcurmolite(Ca,Na)2(UO2)3Mo2(O,OH)11 · nH2O
27.3.12TengchongiteCaO · 6UO3 · 2MoO3 · 12H2OOrth.
27.3.13KamiokiteFe2Mo3O8Hex.
27.3.14FerrimolybditeFe2(MoO4)3 · nH2OOrth. mmm (2/m 2/m 2/m) : Pmmn

Fluorescence of PowelliteHide

Creamy white or yellow to golden yellow (SW UV).

Other InformationHide

Notes:
May replace molybdenite leaving a material with a foliated structure appearance. Alters to Ferrimolybdite.

Decomposed by HCl and HNO3.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for PowelliteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Melville (1891) American Journal of Science: 41: 138.
Koenig and Hubbard (1893) American Journal of Science: 46: 356.
Michel (1894) Bulletin de la Société française de Minéralogie: 17: 612.
Palache, C. (1899) American Journal of Science: 7: 367.
Pilipenko (1915) Bulletin of the Imperial Tomsk University, no. 63 [Min. Abs. (1923): 2: 109].
Larsen, E.S. (1921) The Microscopic Determination of the Nonopaque Minerals, First edition, USGS Bulletin 679: 122.
Zambonini (1923) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 58: 248.
Vegard (1926) Philosophical Magazine and Journal of Science: 1: 1151.
Hintze, Carl (1889) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3B]: 4036.
Pough (1937) American Mineralogist: 22: 57.
Maucher (1938) Zs. Angew. Min.: 1 : 103.
Gianella (1941) University of Nevada Bull. 35, no. 6: 80.
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 1079-1081.
National Bureau of Standards Circular 539 (1956), 6, 22.
Bulletin of the Mineralogical and Geological Society, Prague (1982): 27: 197-200.
Hazen, R.M., L.W. Finger, and J.W.E. Mariathasan (1985) High-pressure crystal chemistry of scheelite-type tungstates and molybdates. Journal of Physical Chemistry Solids, 46, 253–263.
Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2003) Handbook of Mineralogy, Volume V. Borates, Carbonates, Sulfates. Mineral Data Publishing, Tucson, AZ, 813pp.: 563.

Internet Links for PowelliteHide

Localities for PowelliteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListShow

Mineral and/or Locality  
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