Marthozite

Marthozite is an orthorhombic mineral that has a general formula of Cu(UO2)3(SeO3)3(OH)2·7H2O.[3] It was named after Belgian mineralogist Aimé Marthoz (1894-1962), former Director-general of the Union Minière du Haut Katanga - UMHK.[2]

Marthozite
Marthozite crystals in a vug, from Katanga (size: 6.2 x 5.3 x 4.0 cm)
General
CategoryOxide mineral (uranyl selenite)
Formula
(repeating unit)		Cu(UO2)3(SeO3)3(OH)2·7H2O
Strunz classification4.JJ.05
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
(same H-M symbol)
Space groupPbn21
Unit cella = 16.4 Å, b = 17.2 Å,
c = 6.98 Å; Z = 4
Identification
Formula mass1,303.67 g/mol
ColorGreenish brown
Crystal habitBladed
Cleavage{100} perfect, {010} indistinct
Mohs scale hardness6
Specific gravity4.44
Optical propertiesBiaxial (-)
Refractive index1.780 -1.800
Pleochroismyellowish brown to greenish yellow
2V angle39°
DispersionExtreme
Other characteristics Radioactive
References[1][2][3][4]

It is usually found in cavities in selenian (selenium-containing) digenite.[2] It is specifically found in the zones of oxidation of the Musonoi deposit in Katanga, Africa.[5]

Marthozite is orthorhombic, meaning that it has three axes of unequal lengths all orthogonal to each other. Since it is orthorhombic, marthozite is biaxial, meaning that it has three different indices of refraction.[5] Marthozite is anisotropic, which means that it breaks light into one fast ray and one slow ray.[6] Marthozite shows pleochroism from yellowish brown to greenish yellow.[2]

References
  1. Mineralienatlas
  2. Webmineral data
  3. Mindat.org
  4. Handbook of Mineralogy
  5. Fleischer, M. (1970) New mineral names. American Mineralogist, 55, 533.
  6. "Marthozite". Retrieved 5 June 2019.
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