Metazeunerite

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Metazeunerite
Metazeunerite-Quartz-201156.jpg
Metazeunerite crystals to 7 mm on smoky quartz, Erongo Region, Namibia
General
Category Phosphate minerals
Formula
(repeating unit)
Cu(UO2)2(AsO4)2·8H2O
Strunz classification 8.EB.10
Crystal system Tetragonal
Crystal class Dipyramidal (4/m)
(same H-M symbol)
Space group P4/n
Unit cell a = 7.1094 Å, c = 17.416 Å;
Z = 2
Identification
Color Varies from pale to green
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(-)
Refractive index nw=1.643-1.651 nε=1.623-1.635
Birefringence .020
Pleochroism Weak
Other characteristics Radioactive
References [1][2][3]

Metazeunerite is an arsenate mineral with a chemical formula of Cu(UO2)2(AsO4)2·8H2O. The origin of this mineral comes from the dehydration process that metazeunerite must go through, and its association with zeunerite. As dehydration occurs, zeunerite loses an electron and is then metamorphosed into metazeunerite.[4]

Properties[edit]

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.[5][6] When looking at a thin section, metzeunerite is anisotropic, meaning that it has pleochroism. When a mineral is anisotropic, one can see whether it is uniaxial or biaxial, depending on how fast the rays of light are moving through the mineral. This mineral is uniaxial negative due to the ordinary ray being slower than the extraordinary ray.[7]

Occurrence[edit]

Metazeunerite is an uncommon radioactive secondary mineral found in "arsenic bearing hydrothermal uranium deposits" across the world.[8] This widespread mineral occurs specifically in Europe, western North America, Australia, Brazil and Chile, Namibia, and Kazakhstan.[3] It is currently studied through thermal decomposition by calculating the different levels of dehydration, as zeunerite is transformed into metazeunerite.[9]

References[edit]