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(H5O2)Fe3+(SO4)2 · 2H2O
May contain minor As.
Blue, colourless, white, ...
From the Latin, rhombus, rhomb, plus Greek klasis, to break, in allusion to the basal cleavage and crystal form.
A common acidic alteration product of iron sulphides (pyrite, marcasite, pyrrhotite), frequently found as crusts and powders associated with other iron sulphates such as römerite, halotrichite etc.

Classification of Rhomboclase

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
B : With only medium-sized cations

1 : Hydrated Acid Sulfates

25 : Sulphates
10 : Sulphates of Fe alone URL:
Please feel free to link to this page.

Type Occurrence of Rhomboclase

Year of Discovery:
Geological Setting of Type Material:
Pyritic ore body
Associated Minerals at Type Locality:

Occurrences of Rhomboclase

Geological Setting:
Weathering of pyrite rich orebodies, especially in arid climates.

Physical Properties of Rhomboclase

Sub-Vitreous, Pearly
Diaphaneity (Transparency):
Blue, colourless, white, yellow, light green, grey; colourless in transmitted light
Hardness (Mohs):
On {001} perfect; on {110} good.
Conchoidal, Fibrous
2.23 g/cm3 (Measured)    2.21 g/cm3 (Calculated)

Crystallography of Rhomboclase

Crystal System:
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cell Parameters:
a = 9.72Å, b = 18.33Å, c = 5.42Å
a:b:c = 0.53 : 1 : 0.296
Unit Cell Volume:
V 965.67 ų (Calculated from Unit Cell)
Crystals thin tabular {001}, with rhombic outline. Also forms stalactites with a radiating bladed structure.

Optical Data of Rhomboclase

Biaxial (+)
RI values:
nα = 1.534 nβ = 1.553 nγ = 1.638
Measured: 27° , Calculated: 54°
Max Birefringence:
δ = 0.104
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
r > v weak

Chemical Properties of Rhomboclase

(H5O2)Fe3+(SO4)2 · 2H2O

May contain minor As.
Essential elements:
All elements listed in formula:
Analytical Data:
Slowly soluble in water.
Empirical Formula:
HFe3+(SO4)2 · 4H2O

Relationship of Rhomboclase to other Species

7.CB.05Dwornikite(Ni,Fe)SO4 · H2O
7.CB.05GunningiteZnSO4 · H2O
7.CB.05KieseriteMgSO4 · H2O
7.CB.05Poitevinite(Cu,Fe,Zn)SO4 · H2O
7.CB.05SzmikiteMnSO4 · H2O
7.CB.05SzomolnokiteFeSO4 · H2O
7.CB.05CobaltkieseriteCoSO4 · H2O
7.CB.07SanderiteMgSO4 · 2H2O
7.CB.10BonattiteCuSO4 · 3H2O
7.CB.15Aplowite(Co,Mn,Ni)SO4 · 4H2O
7.CB.15Boyleite(Zn,Mg)SO4 · 4H2O
7.CB.15Ilesite(Mn,Zn,Fe)SO4 · 4H2O
7.CB.15RozeniteFeSO4 · 4H2O
7.CB.15StarkeyiteMgSO4 · 4H2O
7.CB.15DrobeciteCdSO4 · 4H2O
7.CB.15CranswickiteMgSO4 · 4H2O
7.CB.20ChalcanthiteCuSO4 · 5H2O
7.CB.20JôkokuiteMnSO4 · 5H2O
7.CB.20PentahydriteMgSO4 · 5H2O
7.CB.20SiderotilFeSO4 · 5H2O
7.CB.25Bianchite(Zn,Fe)SO4 · 6H2O
7.CB.25Chvaleticeite(Mn,Mg)SO4 · 6H2O
7.CB.25FerrohexahydriteFeSO4 · 6H2O
7.CB.25HexahydriteMgSO4 · 6H2O
7.CB.25Moorhouseite(Co,Ni,Mn)SO4 · 6H2O
7.CB.25Nickelhexahydrite(Ni,Mg,Fe)SO4 · 6H2O
7.CB.30RetgersiteNiSO4 · 6H2O
7.CB.35BieberiteCoSO4 · 7H2O
7.CB.35BoothiteCuSO4 · 7H2O
7.CB.35MallarditeMnSO4 · 7H2O
7.CB.35MelanteriteFeSO4 · 7H2O
7.CB.35Zincmelanterite(Zn,Cu,Fe)SO4 · 7H2O
7.CB.35Alpersite(Mg,Cu)[SO4] · 7H2O
7.CB.40EpsomiteMgSO4 · 7H2O
7.CB.40GoslariteZnSO4 · 7H2O
7.CB.40MorenositeNiSO4 · 7H2O
7.CB.45AlunogenAl2(SO4)3 · 17H2O
7.CB.45Meta-alunogenAl2(SO4)3 · 12H2O
7.CB.50AluminocoquimbiteFeAl(SO4)3 · 9H2O
7.CB.55CoquimbiteFe2-xAlx(SO4)3 · 9H2O, x ~0.5
7.CB.55ParacoquimbiteFe2(SO4)3 · 9H2O
7.CB.60KorneliteFe2(SO4)3 · 7H2O
7.CB.65QuenstedtiteFe2(SO4)3 · 11H2O
7.CB.75LishizheniteZnFe2(SO4)4 · 14H2O
7.CB.75RömeriteFe2+Fe23+(SO4)4 · 14H2O
7.CB.80RansomiteCuFe2(SO4)4 · 6H2O
7.CB.85ApjohniteMn2+Al2(SO4)4 · 22H2O
7.CB.85BíliniteFe2+Fe23+(SO4)4 · 22H2O
7.CB.85Dietrichite(Zn,Fe2+,Mn2+)Al2(SO4)4 · 22H2O
7.CB.85HalotrichiteFeAl2(SO4)4 · 22H2O
7.CB.85PickeringiteMgAl2(SO4)4 · 22H2O
7.CB.90MeridianiiteMgSO4 · 11H2O
25.10.1SzomolnokiteFeSO4 · H2O
25.10.2RozeniteFeSO4 · 4H2O
25.10.3SiderotilFeSO4 · 5H2O
25.10.4FerrohexahydriteFeSO4 · 6H2O
25.10.5MelanteriteFeSO4 · 7H2O
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
25.10.13MetahohmanniteFe23+(SO4)2O · 4H2O
25.10.14HohmanniteFe23+(SO4)2O · 8H2O
25.10.15ButleriteFe3+(SO4)(OH) · 2H2O
25.10.16ParabutleriteFe3+(SO4)(OH) · 2H2O
25.10.17AmarantiteFe23+(SO4)2O · 7H2O
25.10.18FibroferriteFe3+(SO4)(OH) · 5H2O
25.10.20RömeriteFe2+Fe23+(SO4)4 · 14H2O
25.10.21BíliniteFe2+Fe23+(SO4)4 · 22H2O
25.10.22CopiapiteFe2+Fe43+(SO4)6(OH)2 · 20H2O

Other Names for Rhomboclase

Name in Other Languages:
Simplified Chinese:板铁矾

Other Information

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 Rhomboclase

Reference List:
Krenner (1891) Ak. Értes., Budapest: 2: 96 (as Rhomboklas).

Scharizer (1901) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 35: 345 (as Saures Ferrisulfate).

Krenner (1907) Földtani Közlöny, Budapest (Magyarhone Földtani Torsulat): 37: 204.

Scharizer (1907) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 43: 113.

Scharizer (1921) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 56: 353.

Posnjak and Merwin (1922) Journal of the American Chemical Society: 44: 1983.

Scharizer (1927) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 65: 335.

Krenner (1928) Centralblatt für Mineralogie, Geologie und Paleontologie, Stuttgart: 265.

Bandy (1938) American Mineralogist: 23: 740.

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: 436-437.

Tschermaks Mineralogische und Petrographische Mitteilungen: 21: 216-232.

Mineralogical Magazine (1974): 39: 611.

American Mineralogist (1995): 80: 408.

Peterson, R. C., Valyashko, E. and Wang, R. (2009): The atomic structure of (H3O)Fe3+(SO4)2 and rhomboclase, (H5O2)Fe3+(SO4)2•2H2O. Can. Mineral. 47, 625-634.

Bolanz, R. (2014): The fate of As5+ during the thermal transformation of As-bearing rhomboclase to (H3O)Fe(SO4)2. 92nd Annual Meeting of the DMG, Jena, Germany, September 21-24. [[programm]=333&tx_coprogramm_pi1[session]=64&tx_coprogramm_pi1[currentPage]=&tx_coprogramm_pi1[action]=programm&tx_coprogramm_pi1[controller]=Source&cHash=98aa4ec242a9518e851e5ddd5090696b]

Internet Links for Rhomboclase

Localities for Rhomboclase

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.
  • Queensland
No reference listed
      • Mount Isa district
Sielecki, R. (1988) The Mount Isa-Cloncurry mineral field. Mineralogical Record, Vol. 19, pg. 469-490.
  • Styria
    • Leutschach
Taucher, J. (1997)
  • Oruro Department
    • Cercado Province
[MinRec 32:476]
[MinRec 32:479]
  • Antofagasta Region
    • El Loa Province
      • Calama
        • Cerritos Bayos
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: 437, 480.; Kampf, A.R.; Mills, S.J.; Housley, R.M.; Williams, P.A.; Dini, M. (2012): Alcaparrosaite, K3Ti4+Fe3+(SO4)4O(H2O)2, a new hydrophobic Ti4+ sulfate from Alcaparrosa, Chile. Mineralogical Magazine 76, 851-861.
  • Xinjiang Autonomous Region
    • Hami Prefecture (Kumul Prefecture; Qumul Prefecture)
      • Hami Co. (Kumul Co.; Qumul Co.)
Xu Ying-xia, Ding Kui-shou, Qin Ke-zhang, Miao Yu, Fang Tong-hui, Xu Xing-wang, and Sun He (2006): Geology in China 33(3), 605-616.
Czech Republic
  • Bohemia (Böhmen; Boehmen)
    • Karlovy Vary Region
      • Krušné Hory Mts (Erzgebirge)
        • Jáchymov District (St Joachimsthal)
Lapis 2002(7/8), 63-65
  • Baden-Württemberg
    • Black Forest
      • Münstertal
        • St Trudpert
Kleinander, R. (2009): Die antimonerzführenden Gänge im Münstergrund bei St. Trudpert. Mineralien-Welt 20 (5), 42-50.
      • Wolfach
        • Oberwolfach
          • Rankach valley
Walenta, K. (1992): Die Mineralien des Schwarzwaldes. Chr. Weise Verlag, München, 336 pp. (in German)
  • Hesse
    • Richelsdorf District
      • Süss
        • Richelsdorf Smelter
S. Weiß: "Mineralfundstellen, Deutschland West", Weise (Munich), 1992
  • Thuringia
    • Gera
      • Ronneburg U deposit
T. Witzke & F. Rüger: Lapis 1998(7/8), 26-64
T. Witzke & F. Rüger: Lapis 1998(7/8), 26-64
  • Attikí Prefecture (Attica; Attika)
    • Lavrion District (Laurion; Laurium)
Kolitsch, U., Rieck, B., Brandstätter, F., Schreiber, F., Fabritz, K. H., Blaß, G. & Gröbner, J. (2014): Neufunde aus dem altem Bergbau und den Schlacken von Lavrion (I). Mineralien-Welt 25 (1), 60-75 (in German). [identification announced; no description given yet]
  • Heves Co.
    • Mátra Mts
      • Gyöngyösoroszi
Farkas, I. M. & Weiszburg, T. G. (2009): Mitt. Österr. Mineral. Ges. 155, 57. (Abs.)
  • Veszprém Co.
    • Balaton Uplands
      • Tapolcai Basin
        • Lesenceistvánd
Handbook of Mineralogy - Anthony, Bideaux, Bladh, Nichols
  • Tuscany
    • Livorno Province
      • Elba Island
        • Capoliveri
J. Göske, T. Witzke, H. Pöllmann, S. Stöber (1997) - Neufunde von Sekundarmineralen in der Lagerstatte Calamita/Insel Elba - Der Aufschluss, 48: 305-313.
  • Pasco department
    • Pasco province
      • Cerro de Pasco
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: 437, 515.
  • Upper Silesia (Śląskie)
    • Upper Silesian Coal Basin
      • Rybnik Coal Area
        • Rybnik
Łukasz Kruszewski (2012) Unique chloride assemblage of exhalative origin from burning coal-mining dump in Radlin (Rybnik Coal Area, S Poland). Mineralogical Society of Poland Special Papers 40
Republic of Macedonia
  • Roszdan
The Canadian Mineralogist Vol.32, pp. 649-665 (1994)
  • Hunedoara Co.
    • Deva
Andrei I. Apopei, Nicolae Buzgar, Gheorghe Damian, and Andrei Buzatu (2014) the Raman Study of Weathering Minerals from the Coranda-Hondol Open Pit (Certej Gold-silver Deposit) and Their Photochemical Degradation Products Under Laser Irradiation. Can Mineral 52:1027-1038.
  • Urals Region
    • Southern Urals
      • Chelyabinsk Oblast'
Cesnokov, B., Kotrly, M. and Nisanbajev, T. (1998): Brennende Abraumhalden und Aufschlüsse im Tscheljabinsker Kohlenbecken - eine reiche Mineralienküche. Mineralien-Welt, 9 (3), 54-63 (in German).
Slovakia (TL)
  • Košice Region
    • Gelnica Co.
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: 437; Mineralogical Magazine (1974): 39: 610.
  • Andalusia
    • Huelva
      • Minas de Riotinto
MinMag 67(2):263-278
A.M.I. Martins specimen
      • Nerva
Romero, A., I. Gonzalez & E. Galan (2006): The role of efflorescent sulfates in the storage of trace elements in stream waters polluted by acid mine-drainage: the case of Pena del Hierro, southwestern Spain. Canadian Mineralogist 44, 1431-1446.
  • Wallis (Valais)
    • Anniviers Valley
      • Saint-Luc
Stalder, H. A., Wagner, A., Graeser, S. and Stuker, P. (1998): "Mineralienlexikon der Schweiz", Wepf (Basel), p. 349.
  • Viloyati Sogd (Viloyati Sughd; Viloyati Khodzhent; Viloyati Leninabad)
    • Zeravshan Range
      • Yagnob River
PXRD (Lukasz Kruszewski)
  • Donetsk (Donets'k) Oblast'
    • Central Donbass
Zanin, Y.N., Pisareva, G.M., Zamirailova, A.G., and Eder, V.G. (2009): Lithology and Mineral Resources 44(3), 267-269
  • Arizona
    • Cochise Co.
      • Mule Mts
        • Warren District
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.:69
            • Calumet and Arizona group of claims (Calumet and Arizona Mining Company group of claims)
Grant, Raymond W., Richard A. Bideaux & Sidney A. Williams (2006), Minerals Added to the Arizona List 1995 to 2005: 3.
Grant, Raymond W., Bideaux, R.A., and Williams, S.A. (2006) Minerals Added to the Arizona List 1995-2005: 7.
            • Queen Hill
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: 531; Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 354, 415; Merwin, H.E. & E. Posnjak (1937), Sulphate encrustations in the Copper Queen mine, Bisbee, AZ, Am.Min.: 22: 567-571; Galbraith, F.W. & D.J. Brennan (1959), Minerals of AZ: 59.
MinRec 12:311
    • Pinal Co.
      • Pinal Mts
        • Pioneer District
          • Superior
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 354, 388.
  • California
    • Inyo Co.
      • Coso Mts (Coso Range)
        • Coso District (New Coso District)
          • Coso Hot Springs
    • Shasta Co.
      • Klamath Mts
        • West Shasta Copper - Zinc District
          • Iron Mountain [town]
            • Iron Mountain
MinRec 22:382; Mineralogical Record 22:381-382; Nordstrom, D. K. and Alpers, C. N. (1999): Negative pH, efflorescent mineralogy, and consequences for environmental restauration at the Iron Mountain Superfund site, California. Proc. Natl. Acad. Sci., USA 96, 3455-3462.; Majzlan, J., Alpers, C. N., Koch, C. B., McCleskey, R. B., Myneni, S. C., & Neil, J. M. (2011). Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California. Chemical Geology, 284(3), 296-305.
Jamieson, H. E., Robinson, C., Alpers, C. N., McCleskey, R. B., Nordstrom, D. K., & Peterson, R. C. (2005). Major and trace element composition of copiapite-group minerals and coexisting water from the Richmond mine, Iron Mountain, California. Chemical Geology, 215(1), 387-405.
  • Georgia
    • Lincoln Co.
Collected by Julian Gray 21 September 2010. Confirmed by XRD at the University of Georgia.
  • Nevada
    • Lander Co.
      • Lewis District
NBMG Spec. Pub. 31 Minerals of Nevada
  • Utah
    • San Juan Co.
      • White Canyon District
        • Red Canyon
          • Chocolate Drop
J. Plášil, A.R. Kampf, A.V. Kasatkin, J. Marty, R. Škoda, S. Silva, J. Čejka (2013): Meisserite, Na5(UO2)(SO4)3(SO3OH)(H2O), a new uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA. Mineral. Mag. 77, 2975-2988
    • Utah Co.
      • East Tintic Mts
UGMS Bull 117 Minerals and Mineral Localities of Utah
  • Virginia
    • Louisa Co.
Minerals of Virginia 1990 by R. V. Dietrich
      • Lake Anna
Minerals of Virginia 1990 by R. V. Dietrich
    • Rockbridge Co.
      • Lyndhurst-Vesuvius District
Minerals of Virginia 1990 by R. V. Dietrich
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