Wulfenite

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Wulfenite
Wulfenite mexique.jpg
Wulfenite from Mexico
General
Category Molybdate mineral
Formula
(repeating unit)
PbMoO4
Strunz classification 07.GA.05
Crystal symmetry Tetragonal dipyramidal
H-M symbol: (4/m)
Space group: I 41/a
Unit cell a = 5.433 Å, c = 12.110 Å; Z=4
Identification
Color Orange-yellow, yellow, honey-yellow, reddish-orange, rarely colorless, grey, brown, olive-green and even black
Crystal habit Thin tabular to pyramidal
Crystal system Tetragonal
Twinning Twins on the [001] common
Cleavage On {011}, distinct; on {001}, {013}, indistinct
Fracture Irregular to sub-conchoidal
Tenacity Brittle
Mohs scale hardness 2.75 - 3
Luster Adamantine, resinous
Streak White
Diaphaneity Transparent to opaque
Specific gravity 6.5-7.0
Optical properties Uniaxial (-), may be anomalously biaxial
Refractive index nω = 2.405 nε = 2.283
Birefringence δ = 0.122
Pleochroism Weak; orange and yellow
Ultraviolet fluorescence None
Other characteristics Specimens may be piezoelectric
References [1][2][3]

Wulfenite is a lead molybdate mineral with the formula PbMoO4. It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore".

It crystallizes in the tetragonal system, often occurring as stubby, pyramidal or tabular crystals. It also occurs as earthy, granular masses. It is found in many localities, associated with lead ores as a secondary mineral associated with the oxidized zone of lead deposits. It is also a secondary ore of molybdenum, and is sought by collectors.

Discovery and occurrence[edit]

Wulfenite was first described in 1845 for an occurrence in Bad Bleiberg, Carinthia, Austria.[1] It was named for Franz Xavier von Wulfen (1728–1805), an Austrian mineralogist.[2]

It occurs as a secondary mineral in oxidized hydrothermal lead deposits. It occurs with cerussite, anglesite, smithsonite, hemimorphite, vanadinite, pyromorphite, mimetite, descloizite, plattnerite and various iron and manganese oxides.[2]

A noted locality for wulfenite is the Red Cloud Mine in Arizona. Crystals are deep red in color and usually very well-formed. The Los Lamentos locality in Mexico produced very thick tabular orange crystals.

Another locality is Mount Peca in Slovenia. The crystals are yellow, often with well-developed pyramids and bipyramids. In 1997, the crystal was depicted on a stamp by the Post of Slovenia.[4]

Gallery[edit]

See also[edit]

References[edit]

  1. ^ a b Mindat
  2. ^ a b c Handbook of Mineralogy
  3. ^ Webmineral data
  4. ^ Gašperšič, Primož. "Rudnik svinca in cinka v Mežici" [Lead and Zinc Mine in Mežica]. In Šmid Hribar, Mateja. Torkar, Gregor. Golež, Mateja. Podjed, Dan. Drago Kladnik, Drago. Erhartič, Bojan. Pavlin, Primož. Jerele, Ines. Enciklopedija naravne in kulturne dediščine na Slovenskem – DEDI (in Slovene). Retrieved 12 March 2012.