Rhomboclase
A valid IMA mineral species - grandfathered
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About Rhomboclase
Formula:
(H5O2)Fe3+(SO4)2 · 2H2O
May contain minor As.
Colour:
Blue, colourless, white, yellow, light green, grey; colourless in transmitted light
Lustre:
Sub-Vitreous, Pearly
Hardness:
2
Specific Gravity:
2.23
Crystal System:
Orthorhombic
Name:
From the Latin, rhombus, rhomb, plus Greek klasis, to break, in allusion to the basal cleavage and crystal form.
Type Locality:
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.
Unique Identifiers
Mindat ID:
3410
Long-form identifier:
mindat:1:1:3410:0
IMA Classification of Rhomboclase
Approved, 'Grandfathered' (first described prior to 1959)
Classification of Rhomboclase
7.CB.55
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
B : With only medium-sized cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
B : With only medium-sized cations
29.1.1.1
29 : HYDRATED ACID AND NORMAL SULFATES
1 : Hydrated Acid Sulfates
29 : HYDRATED ACID AND NORMAL SULFATES
1 : Hydrated Acid Sulfates
25.10.6
25 : Sulphates
10 : Sulphates of Fe alone
25 : Sulphates
10 : Sulphates of Fe alone
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Rbc | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Rhomboclase
Sub-Vitreous, Pearly
Transparency:
Transparent
Colour:
Blue, colourless, white, yellow, light green, grey; colourless in transmitted light
Streak:
White
Hardness:
2 on Mohs scale
Tenacity:
Elastic
Cleavage:
Perfect
On {001} perfect; on {110} good.
On {001} perfect; on {110} good.
Fracture:
Conchoidal, Fibrous
Density:
2.23 g/cm3 (Measured) 2.21 g/cm3 (Calculated)
Optical Data of Rhomboclase
Type:
Biaxial (+)
RI values:
nα = 1.534 nβ = 1.553 nγ = 1.638
2V:
Measured: 27° , Calculated: 54°
Max. Birefringence:
δ = 0.104
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
Surface Relief:
Moderate
Dispersion:
r > v weak
Optical Extinction:
Parallel. X = c; Y = a; Z = b.
Chemistry of Rhomboclase
Mindat Formula:
(H5O2)Fe3+(SO4)2 · 2H2O
May contain minor As.
May contain minor As.
Element Weights:
Elements listed:
Crystallography of Rhomboclase
Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pnma
Cell Parameters:
a = 9.72 Å, b = 18.33 Å, c = 5.42 Å
Ratio:
a:b:c = 0.53 : 1 : 0.296
Unit Cell V:
965.67 ų (Calculated from Unit Cell)
Morphology:
Crystals thin tabular {001}, with rhombic outline. Also forms stalactites with a radiating bladed structure.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0006292 | Rhomboclase | Peterson R C, Valyashko E, Wang R (2009) The atomic structure of (H3O)Fe3+(SO4)2 and rhomboclase, (H5O2)Fe3+(SO4)2*2H2O The Canadian Mineralogist 47 625-634 |  | 2009 | Alcoparrosa, Chile | 0 | 180 |
| 0007142 | Rhomboclase | Majzlan J, Navrotsky A, McCleskey R B, Alpers C N (2006) Thermodynamic properties and crystal structure refinement of ferricopiapite, coquimbite, rhomboclase, and Fe2(SO4)3(H2O)5 European Journal of Mineralogy 18 175-186 | 2006 | synthetic | 0 | 293 | |
| 0015649 | Rhomboclase | Mereiter K (1974) Die Kristallstruktur von Rhomboklas, H5O2+{Fe[SO4]2*2H2O}- Tschermaks Mineralogische und Petrographische Mitteilungen 21 216-232 | 1974 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.18 Å | (> 100) |
| 3.29 Å | (18) |
| 4.05 Å | (15) |
| 3.33 Å | (15) |
| 3.11 Å | (11) |
| 3.05 Å | (10) |
| 4.75 Å | (7) |
Comments:
Cerro de Pasco, Peru. The data are from Van Tassel (1974). Data for synthetic material are also given in that reference.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] | |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) | |
| 56 : Slag and smelter minerals (see also #51 and #55) |
Geological Setting:
Weathering of pyrite rich orebodies, especially in arid climates.
Type Occurrence of Rhomboclase
Geological Setting of Type Material:
Pyritic ore body
Associated Minerals at Type Locality:
Other Language Names for Rhomboclase
Common Associates
Associated Minerals Based on Photo Data:
| 2 photos of Rhomboclase associated with Pyrite | FeS2 |
| 1 photo of Rhomboclase associated with Krausite | KFe(SO4)2 · H2O |
| 1 photo of Rhomboclase associated with Unnamed (Fe Sulphate Hydroxide) | Fe(SO4)(OH) |
| 1 photo of Rhomboclase associated with Butlerite | Fe3+(SO4)(OH) · 2H2O |
| 1 photo of Rhomboclase associated with Hydroniumjarosite | (H3O)Fe3+3(SO4)2(OH)6 |
| 1 photo of Rhomboclase associated with Coquimbite | AlFe3(SO4)6(H2O)12 · 6H2O |
| 1 photo of Rhomboclase associated with Hematite | Fe2O3 |
| 1 photo of Rhomboclase associated with Gypsum | CaSO4 · 2H2O |
| 1 photo of Rhomboclase associated with Zincovoltaite | K2Zn5Fe3+3Al(SO4)12 · 18H2O |
| 1 photo of Rhomboclase associated with Magnesiovoltaite | K2Mg5Fe3+3Al(SO4)12 · 18H2O |
Related Minerals - Strunz-mindat Grouping
| 7.CB. | Sarvodaite | Al2(SO4)3 · 5H2O |
| 7.CB.02 | Voudourisite | CdSO4 · H2O |
| 7.CB.05 | Szmikite | MnSO4 · H2O |
| 7.CB.05 | Szomolnokite | FeSO4 · H2O |
| 7.CB.05 | Cobaltkieserite | CoSO4 · H2O |
| 7.CB.05 | Dwornikite | Ni(SO4) · H2O |
| 7.CB.05 | Kieserite | MgSO4 · H2O |
| 7.CB.05 | Poitevinite | (Cu,Fe)SO4 · H2O |
| 7.CB.05 | Gunningite | ZnSO4 · H2O |
| 7.CB.07 | Sanderite | MgSO4 · 2H2O |
| 7.CB.10 | Bonattite | CuSO4 · 3H2O |
| 7.CB.12 | Belogubite | CuZn(SO4)2 · 10H2O |
| 7.CB.15 | Drobecite | CdSO4 · 4H2O |
| 7.CB.15 | Aplowite | (Co,Mn,Ni)SO4 · 4H2O |
| 7.CB.15 | Cranswickite | MgSO4 · 4H2O |
| 7.CB.15 | Rozenite | FeSO4 · 4H2O |
| 7.CB.15 | Starkeyite | MgSO4 · 4H2O |
| 7.CB.15 | Ilesite | Mn2+(SO4) · 4H2O |
| 7.CB.15 | Boyleite | ZnSO4 · 4H2O |
| 7.CB.20 | Siderotil | FeSO4 · 5H2O |
| 7.CB.20 | Jôkokuite | MnSO4 · 5H2O |
| 7.CB.20 | Pentahydrite | MgSO4 · 5H2O |
| 7.CB.20 | Chalcanthite | CuSO4 · 5H2O |
| 7.CB.25 | Chvaleticeite | Mn(SO4) · 6H2O |
| 7.CB.25 | Nickelhexahydrite | Ni(SO4) · 6H2O |
| 7.CB.25 | Hexahydrite | MgSO4 · 6H2O |
| 7.CB.25 | Bianchite | Zn(SO4) · 6H2O |
| 7.CB.25 | Moorhouseite | Co(SO4) · 6H2O |
| 7.CB.25 | Ferrohexahydrite | FeSO4 · 6H2O |
| 7.CB.30 | Retgersite | NiSO4 · 6H2O |
| 7.CB.35 | Zincmelanterite | (Zn,Cu,Fe)SO4 · 7H2O |
| 7.CB.35 | Melanterite | Fe2+(H2O)6SO4 · H2O |
| 7.CB.35 | Alpersite | (Mg,Cu)(SO4) · 7H2O |
| 7.CB.35 | Bieberite | CoSO4 · 7H2O |
| 7.CB.35 | Boothite | CuSO4 · 7H2O |
| 7.CB.35 | Mallardite | MnSO4 · 7H2O |
| 7.CB.40 | Epsomite | MgSO4 · 7H2O |
| 7.CB.40 | Goslarite | ZnSO4 · 7H2O |
| 7.CB.40 | Morenosite | NiSO4 · 7H2O |
| 7.CB.45 | Meta-alunogen | Al2(SO4)3 · 12H2O |
| 7.CB.45 | Alunogen | Al2(SO4)3 · 17H2O |
| 7.CB.50 | Aluminocoquimbite | Al2Fe2(SO4)6(H2O)12 · 6H2O |
| 7.CB.50 | Lazaridisite | 3CdSO4 · 8H2O |
| 7.CB.52 | Pararaisaite | CuMg[Te6+O4(OH)2] · 6H2O |
| 7.CB.55 | Paracoquimbite | Fe4(SO4)6(H2O)12 · 6H2O |
| 7.CB.55 | Raisaite | CuMg[Te6+O4(OH)2] · 6H2O |
| 7.CB.55 | Coquimbite | AlFe3(SO4)6(H2O)12 · 6H2O |
| 7.CB.57 | Caichengyunite | Fe2+3Al2(SO4)6 · 30H2O |
| 7.CB.60 | Kornelite | Fe2(SO4)3 · 7H2O |
| 7.CB.65 | Quenstedtite | Fe2(SO4)3 · 11H2O |
| 7.CB.70 | Lausenite | Fe2(SO4)3 · 5H2O |
| 7.CB.75 | Römerite | Fe2+Fe3+2(SO4)4 · 14H2O |
| 7.CB.75 | Lishizhenite | ZnFe2(SO4)4 · 14H2O |
| 7.CB.80 | Ransomite | CuFe2(SO4)4 · 6H2O |
| 7.CB.85 | Dietrichite | (Zn,Fe2+,Mn2+)Al2(SO4)4 · 22H2O |
| 7.CB.85 | Halotrichite | FeAl2(SO4)4 · 22H2O |
| 7.CB.85 | Apjohnite | Mn2+Al2(SO4)4 · 22H2O |
| 7.CB.85 | Redingtonite | (Fe2+,Mg,Ni)(Cr,Al)2(SO4)4 · 22H2O |
| 7.CB.85 | Pickeringite | MgAl2(SO4)4 · 22H2O |
| 7.CB.85 | Bílinite | Fe2+Fe3+2(SO4)4 · 22H2O |
| 7.CB.85 | Wupatkiite | (Co,Mg,Ni)Al2(SO4)4 · 22H2O |
| 7.CB.90 | Meridianiite | MgSO4 · 11H2O |
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.
Internet Links for Rhomboclase
mindat.org URL:
https://www.mindat.org/min-3410.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Rhomboclase
Reference List:
Posnjak, E.; Merwin, H. E. (1922) The system, Fe2O3—SO3—H2O. Journal Of The American Chemical Society, 44 (9). 1965-1994 doi:10.1021/ja01430a016p.1983
Bandy, Mark C. (1938) Mineralogy of three sulphate deposits of northern Chile. American Mineralogist, 23 (11) 669-760 p.740
van Tassel, R. (1974) X-ray powder data of rhomboclase. Mineralogical Magazine, 39 (305) 610-612 doi:10.1180/minmag.1974.039.305.18
Mereiter, K. (1974) Die Kristallstruktur von Rhomboklas, H5O2+{Fe[SO4]2·2H2O}-. TMPM Tschermaks Mineralogische und Petrographische Mitteilungen, 21 (3) 216-232 doi:10.1007/bf01081032
Jambor, J.L., Puziewicz, J., Roberts, A.C. (1995) New mineral names. American Mineralogist, 80 (3-4). 404-409
Majzlan, Juraj, Navrotsky, Alexandra, McCleskey, R. Blaine, Alpers, Charles N. (2006) Thermodynamic properties and crystal structure refinement of ferricopiapite, coquimbite, rhomboclase, and Fe2(SO4)3(H2O)5. European Journal of Mineralogy, 18 (2) 175-186 doi:10.1127/0935-1221/2006/0018-0175
Peterson, R. C., Valyashko, E., Wang, R. (2009) The atomic structure of (H3O)Fe3+(SO4)2 and rhomboclase, (H5O2)Fe3+(SO4)2·2H2O. The Canadian Mineralogist, 47 (3) 625-634 doi:10.3749/canmin.47.3.625
Pitman, K. M., Noe Dobrea, E. Z., Jamieson, C. S., Dalton, J. B., Abbey, W. J., Joseph, E. C. S. (2014) Reflectance spectroscopy and optical functions for hydrated Fe-sulfates. American Mineralogist, 99 (8) 1593-1603 doi:10.2138/am.2014.4730
Majzlan, Juraj; Grevel, Klaus-Dieter; Kiefer, Boris; Nielsen, Ulla Gro; Grube, Elisabeth; Dachs, Edgar; Benisek, Artur; White, Mary Anne; Johnson, Michel B. (2017) Thermodynamics and crystal chemistry of rhomboclase, (H5O2)Fe(SO4)2·2H2O, and the phase (H3O)Fe(SO4)2 and implications for acid mine drainage. American Mineralogist, 102 (3). 643-654 doi:10.2138/am-2017-5909
Localities for Rhomboclase
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and 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).
All localities listed without proper references should be considered as questionable.
Australia | |
| Sielecki (1988) |
| Parbhakar-Fox et al. (2014) |
| R Bottrill |
Austria | |
| Taucher (1997) |
Bolivia | |
| Wilson (2001) |
| Wilson (2001) | |
| Jiménez-Franco et al. (2018) |
| Jiménez-Franco et al. (2018) | |
Brazil | |
| Souza et al. (2024) |
Canada | |
| Zodrow (1989) |
| Greengrass et al. (1999) |
Chile | |
| identified by Gerhard Möhn |
| Kampf +5 other references |
| Raman spectroscopy by Joy Desor | |
| Inostroza et al. (2020) | |
| Inostroza et al. (2020) |
China | |
| Xu Ying-xia et al. (2006) |
Costa Rica | |
| Ulloa et al. (2018) |
Czech Republic | |
| Lapis 2002 (7/8) |
Germany | |
| Kleinander (2009) |
| Walenta (1992) |
| Weiß (1990) |
| Schnorrer-Köhler (1988) | |
| Witzke et al. (1998) |
| Witzke et al. (1998) |
Greece | |
| no description given yet] +1 other reference |
| Rieck et al. (2018) |
| Balić-Žunić et al. (2016) |
Hungary | |
| Farkas et al. (2009) |
| Anthony et al. (2016) |
Iceland | |
| Carson (2015) |
| Mineralogy and bulk geochemistry of a ... |
Italy | |
| Italo Campostrini - Università degli ... |
| Ciriotti et al. (2019) |
| Göske et al. (1997) |
| Mauro (2020) |
| Mauro D. (2016) | |
Lebanon | |
| Kruszewski (2019) |
North Macedonia | |
| Percival et al. (1994) |
Peru | |
| Tyc et al. (2022) |
| Tyc et al. (2022) | |
| Palache et al. (1951) |
Poland | |
| Kruszewski (2013) |
| Kruszewski (2012) |
| Kruszewski et al. (2020) |
Portugal | |
| Bobos +2 other references |
| Oliveira et al. (2024) |
Romania | |
| Apopei et al. (2014) +1 other reference |
| A. Januszewska PXRD data / Januszewska et al. (in preparation) |
Russia | |
| Cesnokov et al. (1998) |
| Gas’kova et al. (2008) |
Slovakia (TL) | |
| Palache et al. (1951) +1 other reference |
Spain | |
| Valente et al. (2013) |
| Valente et al. (2013) | |
| Valente et al. (2013) | |
| MinMag 67 (2) |
| Calvo (1999) | |
| Romero et al. (2006) +1 other reference |
Sweden | |
| The Sulfur Problem. Proceedings 8th ... +1 other reference |
Switzerland | |
| Stalder et al. (1998) |
Tajikistan | |
| PXRD (Lukasz Kruszewski) |
Ukraine | |
| Zanin et al. (2009) |
USA | |
| Anthony et al. (1995) |
| Grant et al. (2005) |
| Grant et al. (2005) | |
| Merwin et al. (1937) +3 other references |
| Graeme (1981) | |
| Anthony et al. (1995) +1 other reference |
| |
| King et al. (1991) +3 other references |
| Jamieson et al. (2005) | |
| Collected by Julian Gray 21 September ... |
| Castor et al. (2004) |
| Bullock (1981) |
| Plášil et al. (2013) |
| Bullock (1981) |
| Dietrich (1990) |
| Dietrich (1990) |
| Dietrich (1990) |
Mars | |
| Johnson et al. (2007) +1 other reference |
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Pisciarelli di Agnano, Pozzuoli, Metropolitan City of Naples, Campania, Italy