Mineral Information and Data:

Goethite
FeO(OH) [CNMNC approved formula]

Named in 1806 to honor the German poet, dramatist, and philosopher, Johann Wolfgang von Goethe (1749–1832).

IMA status : Approved Species 1980 ()
CLASSIFICATION 
Dana
(8th edition) :
06.01.01.02  
  (06) Hydroxides and Oxides Containing Hydroxyl
  (06.01) where X+++O OH
  (06.01.01) Diaspore group (Orthorhombic, Pnma or Pnmd)
  
Nickel-Strunz
(10th edition) :
04.FD.10
  (04) Oxides and Hydroxides
  (04.F) Hydroxides (without V or U)
  (04.FD) Hydroxides with OH, without H2O; chains of edge-sharing octahedra
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 4.608 Ǻ, b = 9.956 Ǻ, c = 3.021 Ǻ
Crystal Habit: Crystals prismatic, vertically striated, capillary or acicular in radiating clusters; massive radial, ocherous, colloform
  
Color: Blackish brown, reddish or yellowish brown, brownish
Diaphaneity: Opaque, transparent on thin edges
Luster: Adamantine, Silky, Metallic, Dull
Hardness (Mohs): 5 to 5.5
Measured Density: 3.3 to 4.3 g/cm3
Cleavage: 2; {010} perfect, {100} distinct
Tenacity: Brittle
Fracture: Uneven
Streak: Brownish yellow, yellow-orange, ocher-yellow
  
Polymorphism and Series: Trimorphous with feroxyhyte and lepidocrocite
Geologic Setting: A common weathering product derived from numerous iron-bearing minerals in oxygenated environments; an important component of ore in weathered iron deposits. Also a primary precipitate in hydrothermal, marine, and bog environments upon oxidation of reduced iron-bearing waters.
Mineral Association: Lepidocrocite, hematite, pyrite, siderite, pyrolusite, manganite, many other ironand manganese-bearing species.
  
Synonyms/varieties: Allcharite, limonite (hydrated impure var.)
Other Properties: Gemstone Unlikely Available. BioMineral.

 

Goethite
Origin: Pribram, Bohemia, Czech Republic
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Goethite
Origin: Pribram, Bohemia, Czech Republic
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Goethite
Origin: Warsaw, Hancock Co., Illinois, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Goethite
Origin: Melrose, Iowa, United States
Sample size: 3 x 3 x 3 cm
Photo: Tom Loomis

 

Goethite
(zoom-in of above)

 

Goethite
Origin: Wannatosa, Wisconsin, United States
Sample size: 5 x 4 x 1 cm
Photo: Tom Loomis

 

Goethite
(zoom-in of above)

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