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Mineralpedia Details for Ferrimolybdite

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Ferrimolybdite

Ferrimolybdite

Named for the chemical constituents of ferric iron (ferri), which is iron with the oxidation number 3+, and molybdenum (molybd).  Somewhat uncommon but widespread, Ferrimolybdite can be found in small amounts and as well studied material in localities in Russia, Belgium, the United States, Australia, and China, as well as numerous other, less well studied localities. It occurs in oxidized molybdenum-bearing hydrothermal vein and porphyry deposits as a secondary mineral.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/ferrimolybdite.pdf

Formula
Fe3+2(Mo6+O4)3ยท7H2
Crystal System
Orthorhombic 
Crystal Habit
Earthy, Scaly, Fibrous 
Cleavage
Distinct, None, None 
Luster
Silky 
Color
yellow, canary yellow, sulfur yellow 
Streak
light yellow 
Class
Orthorhombic 
Fracture
Uneven 
Hardness
2.5-3 
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Ferrimolybdite from Lemhi Co., Idaho, United States

Ferrimolybdite
            from Lemhi Co., Idaho, United States

Very rich coverage with faint yellow fibrous crystals throughout Quartz matrix.

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Ferrimolybdite from Little Cottonwood Canyon, Salt Lake Co., Utah, United States

Ferrimolybdite
            from Little Cottonwood Canyon, Salt Lake Co., Utah, United States

Mostly solid Molybdenite with alterations to pulverulent yellow Ferrimolybdite.

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