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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)3ยท7H2O
- 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
- WebMineral
- View Ferrimolybdite
- Mindat
- View Ferrimolybdite
Ferrimolybdite from Lemhi Co., Idaho, United States

Very rich coverage with faint yellow fibrous crystals throughout Quartz matrix.
Ferrimolybdite from Little Cottonwood Canyon, Salt Lake Co., Utah, United States

Mostly solid Molybdenite with alterations to pulverulent yellow Ferrimolybdite.