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Category Oxide mineral
(repeating unit)
Strunz classification 4.FE.40
Dana classification
Crystal system Hexagonal
Unknown space group
Unit cell a = 2.95, c = 4.56 [Å]; Z = 1
Formula mass 88.85 g/mol
Color Brown, yellow-brown
Crystal habit Concretionary, massive, nodular
Streak Yellow
Diaphaneity Opaque
Specific gravity 4.31
Density 4.2
Optical properties Uniaxial
References [1][2][3]

Feroxyhyte is an oxide/hydroxide of iron, δ-Fe3+O(OH). Feroxyhyte crystallizes in the hexagonal system. It forms as brown rounded to concretionary masses. Feroxyhyte is opaque, magnetic, has a yellow streak, and has a relative density of 4.2.[2]

It occurs in manganese-iron nodules on the Atlantic and Pacific Ocean floors. It is also found in the Baltic, White, and Kara Seas.[4] Forms under high pressure conditions and reverts to goethite on exposure to surface conditions.[2] It also occurs as cement and coatings on clasts in poorly drained soils and sediments, formed by the rapid oxidation of iron(II) oxide compounds.[4]

It was first described in 1976 for an occurrence in soils at its type locality: Kolomyya, Ivano-Frankivsk Oblast, Ukraine.[1][4]


  1. ^ a b "Feorxyhyte mineral information and data". Mindat.org. Retrieved 2011-10-24. 
  2. ^ a b c "Feroxyhyte Mineral Data". Webmineral.com. Retrieved 2011-10-24. 
  3. ^ "Information card - FEROXYHYTE". Mineral Crystal Structure Database. Retrieved 2011-10-24. 
  4. ^ a b c Handbook of Mineralogy