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Formula: Fe3+4(V5+O4)4(H2O)2.H2O
Vanadate
Specific gravity: 3.19(2) measured, 3.200 calculated for the empirical formula and 3.263 calculated for the ideal
formula
Hardness: 3½
Streak: Yellow-orange
Colour: Very dark brown, appearing black
Luminescence: Non-fluorescent
Environments
Sedimentary environments
Hydrothermal environments
Mikehowardite is a new mineral, approved in 2020 and to date (June 2022) reported only from the type
locality
Localities
At the type locality, the North Wilson pit, Union Carbide Mine, Wilson Springs, Garland county, Arkansas, USA,
two new secondary minerals, mikehowardite and
donowensite, have been found intimately associated with each other, and
formed by the oxidation of primary ore
vanadium minerals contained in altered sedimentary rocks adjacent to their
contact with a syenite intrusion.
The crystals of mikehowardite are equant prisms, up to about 0.15 mm in diameter, with slightly sloping
terminations
(CM 60.543-554).
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