Metazeunerite: Properties and Occurrences

Metazeunerite is an arsenate mineral with a chemical formula of Cu(UO2)2(AsO4)2·8H2O. It is a mineral consisting of a hydrous arsenate of copper and uranium with less water than zeunerite. The origin of this mineral is almost always from the natural dehydration process of zeunerite. It fluoresces a pastel yellow-green under long-wave and short-wave ultraviolet light.

Named for civil engineer Gustav A. Zeuner who worked at the School of Mines in Freiberg and its lowered hydration state. It was named in 1937 by Aleksandr Evgenievich Fersman and Olga Mikhailovna Shubnikova for “Meta” for a lower hydration state and its relationship to zeunerite.

General Information

  • Category: Phosphate minerals
  • Formula: (repeating unit) Cu(UO2)2(AsO4)2·8H2O
  • Crystal system: Tetragonal
  • Crystal class: Dipyramidal (4/m) (same H-M symbol)
  • Color: Varies from pale to green.

Fig: Metazeunerite Minerals

Properties

Its crystal system is tetragonal and its crystal class is 4/m, which is also called the tetragonal-dipyramidal class because it only has a vertical four-fold rotation axis that is perpendicular to the symmetry plane. This mineral is uniaxial negative due to the ordinary ray being slower than the extraordinary ray.

  • Crystal habit: Tabular rectangular crystals with two pinacoid faces; foliated or micaceous aggregates
  • Twinning Merohedrally: twinned
  • Cleavage: Perfect on {001}; distinct on {010}
  • Fracture: Uneven
  • Tenacity: Brittle
  • Mohs scale hardness: 2-2.5
  • Luster: Vitreous to dull
  • Streak: Pale green
  • Diaphaneity: Transparent to translucent
  • Specific gravity: 3.87
  • Optical properties: Uniaxial(-)

Occurrence

Metazeunerite is an uncommon radioactive secondary mineral found in “arsenic bearing hydrothermal uranium deposits” across the world. This widespread mineral occurs specifically in Europe, western North America, Australia, Brazil and Chile, Namibia, and Kazakhstan.

Many of Metazeunerite’s localities are minor, and few have good specimens, but well-studied material comes from localities in Germany, England, France, the United States, Australia, and Brazil. Metazeunerite is highly radioactive. It is currently studied through thermal decomposition by calculating the different levels of dehydration, as zeunerite is transformed into metazeunerite.

Association: Torbernite, tr¨ogerite, walpurgite, uranospinite, erythrite, mimetite, pharmacosiderite, olivenite, chalcophyllite.

 

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