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Hohmannite

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Formula:
Fe3+2(SO4)2O · 8H2O
Colour:
Brown to burnt orange, light amaranth-red.
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
2.2
Crystal System:
Triclinic
Name:
After Thomas Hohmann (1843–1897), mining engineer of Valparaiso, Chile, discoverer of the species.
Rapidly dehydrates to metahohmannite on exposure to air. Decomposes in hot water.



Classification of Hohmannite

Approved, 'Grandfathered' (first described prior to 1959)
7.DB.30

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
B : With only medium-sized cations; insular octahedra and finite units
31.9.4.1

31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
9 : (AB)(XO4)Zq·xH2O
25.10.14

25 : Sulphates
10 : Sulphates of Fe alone

Physical Properties of Hohmannite

Vitreous
Transparency:
Transparent, Translucent
Comment:
Brilliant
Colour:
Brown to burnt orange, light amaranth-red.
Streak:
Orange-yellow
Hardness:
Cleavage:
Perfect
On {010}, perfect; on {110} and {1_10}, less perfect.
Density:
2.2 g/cm3 (Measured)    

Optical Data of Hohmannite

Type:
Biaxial (-)
RI values:
nα = 1.559 nβ = 1.643 nγ = 1.655
2V:
Measured: 40°
Max Birefringence:
δ = 0.096
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r < v moderate
Pleochroism:
Visible
Comments:
X = Very light yellow
Y = Light greenish yellow
Z = Dark greenish yellow

Chemical Properties of Hohmannite

Formula:
Fe3+2(SO4)2O · 8H2O
IMA Formula:
Fe3+2O(SO4)2 · 8H2O

Crystallography of Hohmannite

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Cell Parameters:
a = 9.05 Å, b = 10.88 Å, c = 7.17 Å
α = 90.15°, β = 90.58°, γ = 107°
Ratio:
a:b:c = 0.832 : 1 : 0.659
Unit Cell V:
675.09 ų (Calculated from Unit Cell)
Morphology:
Crystals short prismatic [001] with faces that are generally rounded and dull or striated. Granular aggregates of subhedral crystals.

Type Occurrence of Hohmannite

Associated Minerals at Type Locality:

Synonyms of Hohmannite

Other Language Names for Hohmannite

Common Associates

Associated Minerals Based on Photo Data:
Amarantite5 photos of Hohmannite associated with Amarantite on mindat.org.
Metahohmannite1 photo of Hohmannite associated with Metahohmannite on mindat.org.

Related Minerals - Nickel-Strunz Grouping

7.DB.05AubertiteCuAl(SO4)2Cl · 14H2O
7.DB.05Magnesioaubertite(Mg,Cu)Al(SO4)2Cl · 14H2O
7.DB.05Svyazhinite(Mg,Mn2+,Ca)(Al,Fe3+)(SO4)2F · 14H2O
7.DB.10KhademiteAl(SO4)F · 5H2O
7.DB.10RostiteAl(SO4)(OH) · 5H2O
7.DB.15JurbaniteAl(SO4)(OH) · 5H2O
7.DB.20Minasragrite(V4+O)(SO4) · 5H2O
7.DB.20Orthominasragrite(V4+O)(SO4) · 5H2O
7.DB.20Anorthominasragrite(V4+O)(SO4) · 5H2O
7.DB.25Bobjonesite(V4+O)(SO4) · 3H2O
7.DB.30AmarantiteFe3+2(SO4)2O · 7H2O
7.DB.30MetahohmanniteFe3+2(SO4)2O · 4H2O
7.DB.35AluminocopiapiteAl2/3Fe3+4(SO4)6(OH)2 · 20H2O
7.DB.35CalciocopiapiteCaFe4(SO4)6(OH)2 · 10H2O
7.DB.35CopiapiteFe2+Fe3+4(SO4)6(OH)2 · 20H2O
7.DB.35CuprocopiapiteCuFe4(SO4)6(OH)2 · 20H2O
7.DB.35FerricopiapiteFe5(SO4)6O(OH) · 20H2O
7.DB.35MagnesiocopiapiteMgFe3+4(SO4)6(OH)2 · 20H2O
7.DB.35ZincocopiapiteZnFe3+4(SO4)6(OH)2 · 18H2O

Related Minerals - Hey's Chemical Index of Minerals Grouping

25.10.1SzomolnokiteFeSO4 · H2O
25.10.2RozeniteFeSO4 · 4H2O
25.10.3SiderotilFeSO4 · 5H2O
25.10.4FerrohexahydriteFeSO4 · 6H2O
25.10.5MelanteriteFeSO4 · 7H2O
25.10.6Rhomboclase(H5O2)Fe3+(SO4)2 · 2H2O
25.10.7LauseniteFe2(SO4)3·5H2O
25.10.8KorneliteFe2(SO4)3 · 7H2O
25.10.9CoquimbiteFe2-xAlx(SO4)3 · 9H2O, x ~0.5
25.10.10ParacoquimbiteFe2(SO4)3 · 9H2O
25.10.11QuenstedtiteFe2(SO4)3 · 11H2O
25.10.12FerricopiapiteFe5(SO4)6O(OH) · 20H2O
25.10.13MetahohmanniteFe3+2(SO4)2O · 4H2O
25.10.15ButleriteFe3+(SO4)(OH) · 2H2O
25.10.16ParabutleriteFe3+(SO4)(OH) · 2H2O
25.10.17AmarantiteFe3+2(SO4)2O · 7H2O
25.10.18FibroferriteFe3+(SO4)(OH) · 5H2O
25.10.19Hydroniumjarosite(H3O)Fe3+3(SO4)2(OH)6
25.10.20RömeriteFe2+Fe3+2(SO4)4 · 14H2O
25.10.21BíliniteFe2+Fe3+2(SO4)4 · 22H2O
25.10.22CopiapiteFe2+Fe3+4(SO4)6(OH)2 · 20H2O

Other Information

Notes:
Once exposed it dehydrates and crumbles to metahohmannite.

Decomposed by hot water but virtually insoluble in cold water. Readily soluble in HCl.
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 Hohmannite

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Frenzel (1887) Mineralogische und petrographische Mitteilungen, Vienna: 9: 397.
Frenzel (1890) Mineralogische und petrographische Mitteilungen, Vienna: 11: 215.
Darapsky (1890) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, Heidelberg, Stuttgart: I: 56.
Darapsky (1890) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, Heidelberg, Stuttgart: II: 267 (as Castanite).
Hintze, Carl (1889) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3B]: 4426.
Rogers (1931) American Mineralogist: 16: 396.
Ungemach (1935) Bulletin de la Société française de Minéralogie: 58: 97.
Bandy (1938) American Mineralogist: 23: 746.
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 613-614.
Scordari, F. (1978): The crystal structure of hohmannite, Fe2(H2O)4[(SO4)2O]·4(H2O) and its relationship to amarantite, Fe2(H2O)4[(SO4)2O]·3(H2O). Mineralogical Magazine 42, 144-146.
Scordari, F., Ventruti, G., Gualtieri, A. F. (2004): The structure of metahohmannite, Fe23+[O(SO4)2].4H2O, by in situ synchrotron powder diffraction. American Mineralogist 89, 365-370.

Internet Links for Hohmannite

mindat.org URL:
https://www.mindat.org/min-1918.html
Please feel free to link to this page.

Localities for Hohmannite

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Argentina
 
  • San Juan
    • Calingasta Department
      • Calingasta
        • Quebrada Alcaparrosa
Notulae Naturae of The Academy of Natural Sciences of Philadelphia, # 89 (1941).
Chile (TL)
 
  • Antofagasta Region
    • Antofagasta Province
(Tschermaks) Min.Mitt. (1887): 9: 397; Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 614.
    • El Loa Province
      • Calama
        • Chuquicamata District
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 608, 614.
          • Toki Cu deposit (Toki Cluster)
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 614.
  • Tarapacá Region
    • El Tamarugal Province
      • Pampa del Tamarugal
Peter G. Seroka collection
Greece
 
  • Attikí Prefecture (Attica; Attika)
    • Lavrion District (Laurion; Laurium)
      • Lavrion District Mines
        • Plaka
          • Plaka Mines
Möckel, S. (2001): Wallkilldellit und weitere acht Neubestimmungen aus Lavrion, Griechenland. Lapis 26 (11), 43.
Branko Rieck Collection
USA
 
  • California
    • Napa Co.
      • Knoxville District
        • Knoxville
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 614; Rogers, Austin Flint (1931b), Castanite, a basic ferric sulphate from Knoxville, California: American Mineralogist: 16: 396; Bandy, Mark C. (1932), Castanite from Chuquicamata, Chile: American Mineralogist: 17: 534-537; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 273.
Mineral and/or Locality  
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