Ferrimolybdite
specimen number:
2262092
location:
Mohave Co., Arizona, USA
description: Ferrimolybdite is a secondary hydrated iron molybdenum oxide mineral that typically forms through the oxidation of primary molybdenite. Geologically, it occurs in the oxidized zones of molybdenum-bearing hydrothermal deposits, often appearing as distinct canary-yellow to sulfur-yellow fibrous crusts, earthy coatings, or radiating acicular microcrystals. While not a primary target for mining or quarrying due to its occurrence in relatively small quantities, it serves as an important indicator mineral for prospectors and geologists identifying underlying ore bodies. Historically, ferrimolybdite has been documented at numerous global localities, including the Climax and Henderson mines in Colorado and the Knaben mine in Norway, with records of its identification dating back to the early 20th century when it was often confused with molybdite. Significant study and collection of the mineral accompanied the peak industrial production of molybdenum during the mid-1900s and continues in active and historic mining districts through 2026. Its presence remains a key geological marker for understanding the geochemical weathering processes of sulfide-rich deposits in varied environmental conditions.
Yellow micro crystals and masses of ferrimolydite throughout matrix. Good example for the species.
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