Pyroaurite (original) (raw)
A valid IMA mineral species - grandfathered
About PyroauriteHide
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Formula:
Mg6Fe3+2(OH)16[CO3] · 4H2O
Colour:
Yellow to brownish-white, white, gray, silver-white, greenish or colourless
Lustre:
Vitreous, Waxy, Pearly
Specific Gravity:
2.1 - 2.14
Name:
Named in 1865 by Lars Johan Igelström from the Greek πυροζ for "fire" and the Latin aurum for "gold" in allusion to the golden-yellow colour assumed by the mineral on heating at relatively low temperatures. Pyroaurite was first found at Långban, Värmland, Sweden.
Later, XRD studies of the type material showed it to contain coexisting hexagonal and rhombohedral phases (Aminoff and Broome 1933). Frondel (1941) reserved the name pyroaurite for the hexagonal phase, and Sjögrenite was introduced for the rhombohedral phase.
In 2012, the hydrotalcite super-group was redefined by S. J. Mills, A. G. Christy, J. M. R. Genin, T. Kameda, and F. Colombo. Pyroaurite was redefined incorporating the former sjögrenite with two polytypes, pyroaurite-3R (formerly pyroaurite, sensu lato) and pyroaurite-2H (formerly sjögrenite). Both polytypes may occur in a single crystal, with the 2H phase at the core and the 3R phase at the rim (Almann 1968, cited after Mills et al. 2012).
Unique IdentifiersHide
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Long-form identifier:
mindat:1:1:3330:1
1741f400-ac47-4a52-9509-3bb9f294444d
IMA Classification of PyroauriteHide
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Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Mg6Fe3+2(CO3)(OH)16 · 4H2O
Classification of PyroauriteHide
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5.DA.50
5 : CARBONATES (NITRATES)
D : Carbonates with additional anions, with H2O
A : With medium-sized cations
16b.6.2.3
16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
6 : AmBn(XO3)pZq
xH2O & with (m+n):p = 8:1
11.13.2
11 : Carbonates
13 : Carbonates of Fe
Mineral SymbolsHide
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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference |
|---|---|---|
| Pya | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Pya | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
| Pya | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Physical Properties of PyroauriteHide
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Colour:
Yellow to brownish-white, white, gray, silver-white, greenish or colourless
Density:
2.1 - 2.14 g/cm3 (Measured) 2.12 g/cm3 (Calculated)
Optical Data of PyroauriteHide
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RI values:
_n_ω = 1.564 _n_ε = 1.543
δ = 0.021
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Comments:
O = pale yellowish, brownish, reddish
E = colourless
Chemistry of PyroauriteHide
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Mindat Formula:
Mg6Fe3+2(OH)16[CO3] · 4H2O
Common Impurities:
Cr,Al,Mn
Crystallography of PyroauriteHide
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Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
| Pyroaurite-2H | Pyroaurite-3R |
|---|---|
| Mg6Fe3+2(OH)16(CO3) · 4H2O | Mg6Fe3+2(OH)16(CO3) · 4H2O |
| Hexagonal | Trigonal |
| 6/m m m _(_6/_m_2/_m_2/m ) - Dihexagonal Dipyramidal | 3_m_ _(_32/m ) - Hexagonal Scalenohedral |
| _P_63/m m c | R_3_m |
| a = 3.113(3) Å, c = 15.61(1) Å | a = 3.1094(2) Å, c = 23.4117(9) Å |
| a:c = 1 : 5.014 | a:c = 1 : 7.529 |
| V 131.01 ų(Calculated from Unit Cell) | V 196.03 ų(Calculated from Unit Cell) |
Crystal StructureHide
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| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014447 | Pyroaurite | Ingram L, Taylor H F W (1967) The crystal structures of sjoegrenite and pyroaurite Mineralogical Magazine 36 465-479 |  |
1967 | Sweden | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder DiffractionHide
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Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.6 Å | (10) |
| 3.89 Å | (7) |
| 2.62 Å | (4) |
| 2.33 Å | (4) |
| 1.981 Å | (5) |
| 1.556 Å | (2) |
| 1.526 Å | (2) |
Comments:
Powder pattern indistinguishable from that of desautelsite (Mn3+-analogue).
Geological EnvironmentHide
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Geological Setting:
In serpentinites and magnesian skarns.
Type Occurrence of PyroauriteHide
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Synonyms of PyroauriteHide
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Other Language Names for PyroauriteHide
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Varieties of PyroauriteHide
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Relationship of Pyroaurite to other SpeciesHide
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Other Members of this group:
| Desautelsite | Mg6Mn3+2(OH)16[CO3] · 4H2O | Trig. 3_m_ _(_32/m ) |
|---|---|---|
| Droninoite | Ni6Fe3+2(OH)16Cl2 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Hydrotalcite | Mg6Al2(CO3)(OH)16 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Hydrotalcite-3R | Mg6Al2(CO3)(OH)16 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Iowaite | Mg6Fe3+2(OH)16Cl2 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Kaznakhtite | Ni6Co3+2(CO3)(OH)16 · 4H2O | Trig. 3 : _R_3 |
| Meixnerite | Mg6Al2(OH)16(OH)2 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Reevesite | Ni6Fe3+2(OH)16(CO3) · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Stichtite | Mg6Cr3+2(OH)16[CO3] · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| Takovite | Ni6Al2(OH)16[CO3] · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
| UM2002-02-COH:FeNi | (Fe2+,Ni)6Fe3+2(CO3)(OH)16 · 4H2O | |
| Woodallite | Mg6Cr2(OH)16Cl2 · 4H2O | Trig. 3_m_ _(_32/m ) : R_3_m |
Common AssociatesHide
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Associated Minerals Based on Photo Data:
Related Minerals - Strunz-mindat GroupingHide
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Other InformationHide
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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 PyroauriteHide
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References for PyroauriteHide
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Reference List:
Mills, S. J., Christy, A. G., Génin, J.-M. R., Kameda, T., Colombo, F. (2012) Nomenclature of the hydrotalcite supergroup: natural layered double hydroxides. Mineralogical Magazine, 76 (5) 1289-1336 doi:10.1180/minmag.2012.076.5.10
Localities for PyroauriteHide
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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.
Locality ListHide
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- 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). 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 (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.