Marthozite is an

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

that has a general formula of Cu(UO₂)₃(SeO₃)₃(OH)₂·7H₂O. It was named after Belgian mineralogist Aimé Marthoz (1894–1962), former Director-general of the Union Minière du Haut Katanga - UMHK. It is usually found in cavities in selenian ( selenium-containing)

digenite Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal - hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic fo ...

. It is specifically found in the zones of oxidation of the Musonoi deposit in Katanga,

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

.Fleischer, M. (1970) New mineral names. American Mineralogist, 55, 533. Marthozite is

, meaning that it has three axes of unequal lengths all

orthogonal In mathematics, orthogonality is the generalization of the geometric notion of ''perpendicularity''. By extension, orthogonality is also used to refer to the separation of specific features of a system. The term also has specialized meanings in ...

to each other. Since it is orthorhombic, marthozite is biaxial, meaning that it has three different indices of refraction. Marthozite is

anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...

, which means that it breaks light into one fast ray and one slow ray. Marthozite shows pleochroism from yellowish brown to greenish yellow.

References

Copper(II) minerals Tellurite and selenite minerals Uranium(VI) minerals Orthorhombic minerals Minerals in space group 33 {{oxide-mineral-stub