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Söhngeite

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About SöhngeiteHide

A. P. Gerhard Söhnge
Formula:
Ga(OH)3
Colour:
Brown, white,pale yellow, pale brown, pale greenish yellow
Hardness:
4 - 4½
Specific Gravity:
3.84
Crystal System:
Tetragonal
Name:
Named in 1965 by H. Strunz in honor of Adolf Paul Gerhard Söhnge (10 November 1913, Saron, Western Cape, South Africa - 14 July 2006), chief geologist, Tsumeb corporation, Tsumeb, Namibia, who discovered the mineral. He was also a professor at the Stellenbosch University (1968-1978).
Söhngeite Group. The Ga analogue of bernalite and dzhalindite. One of a very few approved minerals with species-defining gallium; compare gallite, tsumgallite, gallobeudantite and galloplumbogummite.

Structurally a hydroxide perovskite. The structure has 5 independent OH groups and is based on Ga(OH)6 octahedra.


Classification of SöhngeiteHide

Approved
Approval Year:
1965
4.FC.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
C : Hydroxides with OH, without H2O; corner-sharing octahedra
6.3.5.2

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
3 : X(OH)3
7.7.1

7 : Oxides and Hydroxides
7 : Oxides of Group III metals other than Al

Physical Properties of SöhngeiteHide

Transparency:
Transparent
Colour:
Brown, white,pale yellow, pale brown, pale greenish yellow
Comment:
Semitransparent
Hardness:
4 - 4½ on Mohs scale
Density:
3.84 g/cm3 (Measured)    3.847 g/cm3 (Calculated)

Optical Data of SöhngeiteHide

Type:
Isotropic
RI values:
n = 1.736
Birefringence:
Isotropic minerals have no birefringence
Surface Relief:
High

Chemical Properties of SöhngeiteHide

Formula:
Ga(OH)3

Crystallography of SöhngeiteHide

Crystal System:
Tetragonal
Cell Parameters:
a = 7.4546 Å, c = 7.3915 Å
Ratio:
a:c = 1 : 0.992
Unit Cell V:
410.75 ų (Calculated from Unit Cell)
Twinning:
trillings of composite flattened, curved crystals; interpenetrant at right angles according to an unknown
law
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

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
3.74 (100)
1.669 (70)
2.63 (60)
1.525 (60)
1.867 (40)
2.15 (35)
2.36 (30)

Type Occurrence of SöhngeiteHide

General Appearance of Type Material:
crystalline, twinned groups and aggregates, up to 1 cm; single crystals are very rare
Geological Setting of Type Material:
oxidation product of gallite-bearing germanite ore, within an oxidation zone of a hydrothermal polymetallic deposit
Associated Minerals at Type Locality:

Synonyms of SöhngeiteHide

Other Language Names for SöhngeiteHide

German:Sohngeit
Spanish:Sohngeita

Relationship of Söhngeite to other SpeciesHide

Other Members of this group:
BernaliteFe(OH)3 · nH2O (n = 0.0 to 0.25)Orth. mmm (2/m 2/m 2/m) : Pmmn
DzhalinditeIn(OH)3Iso.

Related Minerals - Nickel-Strunz GroupingHide

4.FC.05BernaliteFe(OH)3 · nH2O (n = 0.0 to 0.25)Orth. mmm (2/m 2/m 2/m) : Pmmn
4.FC.05DzhalinditeIn(OH)3Iso.
4.FC.10BurtiteCa[Sn(OH)6]Iso.
4.FC.10Mushistonite(Cu,Zn,Fe2+)[Sn(OH)6]
4.FC.10NataniteFe2+[Sn(OH)6]Iso. m3m (4/m 3 2/m) : Pn3m
4.FC.10SchoenfliesiteMg[Sn(OH)6]Iso. m3 (2/m 3) : Pn3
4.FC.10VismirnoviteZn[Sn(OH)6]Iso.
4.FC.10WickmaniteMn2+[Sn(OH)6]Iso. m3 (2/m 3) : Pn3
4.FC.15JeanbandyiteFe3+xFe2+1-xSn(OH)6-xOx (1 ≥ x > 0.5)Tet. 4/m : P42/n
4.FC.15MopungiteNa[Sb5+(OH)6]Tet. 4/m : P42/n
4.FC.15StottiteFe2+[Ge4+(OH)6]Tet.
4.FC.15TetrawickmaniteMn2+[Sn4+(OH)6]Tet. 4/m : P42/n
4.FC.20Ferronigerite-2N1S(Al,Fe,Zn)2(Al,Sn)6O11(OH)Trig. 3m (3 2/m) : P3m1
4.FC.20Magnesionigerite-6N6S(Mg,Al,Zn)3(Al,Sn,Fe)8O15(OH)Trig. 3m (3 2/m) : R3m
4.FC.20Magnesionigerite-2N1S(Mg,Al,Zn)2(Al,Sn)6O11(OH)Trig. 3m (3 2/m) : P3m1
4.FC.20Ferronigerite-6N6S(Al,Fe,Zn)3(Al,Sn,Fe)8O15(OH)Trig. 3m (3 2/m) : R3m
4.FC.20Zinconigerite-2N1S(Zn,Al,Mg)2(Al,Sn)6O11(OH)Trig. 3m (3 2/m) : P3m1
4.FC.20Zinconigerite-6N6S(Zn,Mg,Al)3(Al,Sn,Fe)8O15(OH)Trig. 3m (3 2/m) : R3m
4.FC.25Magnesiotaaffeite-6N’3SMg2BeAl6O12Trig.
4.FC.25Magnesiotaaffeite-2N’2SMg3Al8BeO16Hex. 6/mmm (6/m 2/m 2/m)

Related Minerals - Dana Grouping (8th Ed.)Hide

6.3.5.1DzhalinditeIn(OH)3Iso.
6.3.5.3BernaliteFe(OH)3 · nH2O (n = 0.0 to 0.25)Orth. mmm (2/m 2/m 2/m) : Pmmn

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

7.7.2Cerianite-(Ce)(Ce4+,Th)O2Iso. m3m (4/m 3 2/m) : Fm3m
7.7.3AvicenniteTl2O3Iso. m3 (2/m 3) : Ia3
7.7.4DzhalinditeIn(OH)3Iso.

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for SöhngeiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Strunz, H. (1965) Söhngeit, Ga(OH)3, ein neues Mineral. Naturwissenschaften: 52: 493 (in German).
Fleischer, M. (1966) New mineral names. American Mineralogist: 51: 1815-1820.
Scott, J.D. (1971) Crystal structure of a new mineral, söhngeite. American Mineralogist: 56: 355-355.
Welch, M.D., Kleppe, A.K. (2016) Polymorphism of the hydroxide perovskite Ga(OH)3 and possible proton-driven transformational behaviour. Physics and Chemistry of Minerals: 43, 515-526.
Anthony, J.W., Bideaux, R.A., Bladh, K.W., Nichols, M.C., Eds. Handbook of Mineralogy, Mineralogical Society of America, Chantilly, VA 20151-1110, USA. http://www.handbookofmineralogy.org/ (2016)
Mitchell, R.H., Welch, M.D., Chakhmouradian, A.R. (2017) Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition. Mineralogical Magazine: 81: 411-461.

Internet Links for SöhngeiteHide

Localities for SöhngeiteHide

ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Namibia (TL)
 
  • Oshikoto Region (Otjikoto Region)
    • Tsumeb
Naturwissenschaften (1965): 52: 493; American Mineralogist (1966): 51: 1815.
Mineral and/or Locality  
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