Söhngeite

Ga(OH)3
IMA status
  • Approved
IMA symbol
Söh
Discovered
1965
IMA approved
1965
Also known as
  • IMA1965-022
  • Söhngeiet

Where it forms, where it's found

Geological setting

The oxidation product of gallite-bearing germanite ore, within an oxidation zone of a hydrothermal polymetallic deposit.

Type locality
Tsumeb Mine (Ongopolo Mine)
  1. Tsumeb
  2. Oshikoto Region
  3. Namibia

-19.2270°, 17.7276°

1recorded occurrences
Source · OpenStreetMap

Physical

Hardness
123456789104 – 4.5/ 10 MOHS
  1. 1Talc
  2. 2Gypsum
  3. 3Calcite
  4. 4Fluorite
  5. 5Apatite
  6. 6Orthoclase
  7. 7Quartz
  8. 8Topaz
  9. 9Corundum
  10. 10Diamond
Transparency
Transparent
Colour
Brown · white · pale yellow · pale brown · pale greenish yellow

Semitransparent

Density
3.84 g/cm³

Optical

Optical type
Isotropic
Surface relief
High
Principal indices
n 1.736

Crystallography

Crystal system
Tetragonal
Cell parameters
a = 7.4546 Å · c = 7.3915 Å
Twinning

Trillings of composite flattened, curved crystals; interpenetrant at right angles according to an unknown law.

Type-locality form

Crystalline, twinned groups and aggregates, up to 1 cm; single crystals are very rare.

Comment

P42/nmc or P42/n (both refinements give good results); previously thought to be orthorhombic (pseudocubic), Pmn21, but this was shown to be unlikely for a hydroxide perovskite

Crystal structure

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
31GaGalliumGallium169.72369.723
57.75%
8OOxygenOxygen315.99947.997
39.75%
1HHydrogenHydrogen31.0083.024
2.50%
Total120.744100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • IMA1965-022
  • Söhngeiet

In other languages

German
IMA 1965-022 · Söhngeit
Italian
Söhngeite

Classification

Strunz
10th ed.

4.FC.05

  • 4OxidesClass
  • 4.FHydroxides (without V or U)Division
  • 4.FCHydroxides with OH, without H2O; corner-sharing octahedraGroup
  • 4.FC.05SöhngeiteSpecies
Dana
8th ed.

06.03.05.02

  • 06Hydroxides and Oxides Containing HydroxylClass
  • 06.03X(OH)3Type
  • 06.03.05Dzhalindite GroupGroup
  • 06.03.05.02SöhngeiteSpecies
CIM
—

7.7.1

  • 7Oxides and HydroxidesClass
  • 7.7Oxides of Group III metals other than AlGroup
  • 7.7.1SöhngeiteSpecies

Group, growth & confusion

In the same group
2 members

Literature, links & citation

Citations
  1. 1965Strunz, H. (1965) Söhngeit, Ga(OH)3, ein neues Mineral. Die Naturwissenschaften, 52 (17). 493 doi:10.1007/bf00646572DOI: 10.1007/bf00646572
  2. 1966Fleischer, Michael (1966) New Mineral Names. American Mineralogist, 51 (11-12) 1815-1820
  3. 1971Scott, J.D. (1971) Crystal structure of a new mineral, söhngeite. American Mineralogist: 56: 355-355.
  4. 2005(2005) Söhngeite. Handbook of Mineralogy. Mineralogical Society of America
  5. 2016Anthony, John W., Bideaux, Richard A., Bladh, Kenneth W., Nichols, Monte C. - Eds. (2016) Handbook of Mineralogy. https://www.handbookofmineralogy.org/
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Söhngeite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/sohngeite-3709},
  note      = {Accessed 2026-05-11}
}