Constituent
Name
Goethite
IMA name
Goethite
Class
non-silicate mineral
Compound type
oxide-hydroxide
Constituent abundance in material
Relevance
main - major
Arrangement
single phase
Mass fraction
1.0 $\pm$ 0.01
Chemical composition
Formula
$FeO(OH)$
Chemical formula
FeO(OH)
Elemental formula
(Fe3+) O2 H
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Fe^{3+}$ Iron(III) cation element 1 constituent element main
$O$ Oxygen element 1 constituent element main
$(OH)^-$ Hydroxide anion chemical function 1 anionic radical main
Composition comments
Common impurities: Mn
Chemical functions
  Function Number
$(OH)^-$ 1
Chemical bonds
  Bond Number
$O^--H$ 1
Oxides
Formula $Fe_{2}O_{3}$ $H_{2}O$
Mass fraction (%) 89.86 10.14

Strunz

Class
oxides - hydroxides - arsenites (04)
Division
hydroxides (without V or U) (04.F)
Family
Hydroxides with OH, without H2O; chains of edge-sharing octahedra (04.FD)
Code
04.FD.10

Dana

Major class
oxides and hydroxides (III)
Class
hydroxides and oxides containing hydroxyl (06)
Type
where X+++O OH (06.01)
Group
Diaspore group (Orthorhombic, Pnma or Pnmd) (06.01.01)
Code
06.01.01.02
Phase name
alpha-FeO(OH)
Phase type
crystalline
Crystal system
orthorhombic
Crystal class
dipyramidal
Crystal class symbol
mmm (D2h)
Crystal spacegroup
Pnma
Texture
cryptocrystalline
Molar mass
88.85 $g/mol$
Density
3.3 - 4.3 $g/cm^3$
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.138 - 0.24
Refraction index $n_{\alpha}$
2.26 - 2.275
Refraction index $n_{\beta}$
2.393 - 2.409
Refraction index $n_{\gamma}$
2.398 - 2.515
Dispersion V
0 - 27
Color
brown, reddish brown, yellowish brown, brownish yellow
Diaphaneity
subtranslucent to opaque