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Beraunite
A valid IMA mineral species - grandfathered
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About Beraunite
Beroun (Beraun), Czech Republic
Formula:
Fe3+6(PO4)4O(OH)4 · 6H2O
Colour:
Dark red, reddish, brown-red
Lustre:
Resinous, Pearly
Hardness:
3 - 4
Specific Gravity:
2.8 - 3.08
Crystal System:
Monoclinic
Member of:
Name:
Named by August Breithaupt in 1840 for the town of Beroun (Beraun) near the type locality at the Hrbek Mine, Svatá Dobrotivá (St Benigna), Beroun (Beraun), Bohemia, Czech Republic. Beraunite was redefined by Fanfani and Zanazzi (1967), on the basis of a crystal structural analysis, as a mixed-valence iron phosphate and they left the original fully oxidized end-member unnamed. In essence, they had discovered a new mineral species (ferroberaunite; later defined by Tvrdý et al., 2021) but they re-used an existing name for a different composition (beraunite). Eleonorite was later defined by Chukanov et al. (2017) as the oxidized end-member of the beraunite-ferrobraunite series (previously also called "oxyberaunite") but is now discredited. Both beraunite and eleonorite had previously been applied to the fully oxidized mineral. Subsequently, Vrtiška et al. (2022), based on a restudy of the type material, redefined beraunite as the oxidised phase and discredited eleonorite.
A secondary mineral found in bog iron ores and phosphate deposits, plus as a cement in clays, sands, and bone material; also as an alteration product of triphylite in granitic pegmatites.
The name beraunite is now applied only to the fully oxidised species (see redefinition by Vrtiška et al., 2022) and the name ferroberaunite should be applied to the mixed-valence (both Fe2+ and Fe3+) species.
Note: beraunite is always more or less reddish, while ferrobraunite is greenish.
May be confused with acicular oxidised dufrénite and natrodufrénite.
The name beraunite is now applied only to the fully oxidised species (see redefinition by Vrtiška et al., 2022) and the name ferroberaunite should be applied to the mixed-valence (both Fe2+ and Fe3+) species.
Note: beraunite is always more or less reddish, while ferrobraunite is greenish.
May be confused with acicular oxidised dufrénite and natrodufrénite.
Unique Identifiers
Mindat ID:
628
Long-form identifier:
mindat:1:1:628:6
Similar Names
| Barronite | A valid IMA mineral species | (◻0.5Ba0.5)(UO2)2Si5O12(OH) · 2H2O |
| Birunite | A valid IMA mineral species - grandfathered - questionable | Ca18(SiO3)8.5(CO3)8.5SO4 · 15H2O(?) |
| Bornite | A valid IMA mineral species - grandfathered | Cu5FeS4 |
| Bornite (of Pinkerton) | A rock subtype | |
| Braunite | A valid IMA mineral species - grandfathered | Mn2+Mn63+(SiO4)O8 |
| Braunite-II | Valid as an unnamed mineral | Ca(Mn3+,Fe)14(SiO4)O20 |
| Brianite | A valid IMA mineral species | Na2CaMg(PO4)2 |
IMA Classification of Beraunite
Approved, 'Grandfathered' (first described prior to 1959)
IMA status notes:
Redefined by the IMA
IMA Formula:
Fe3+6(PO4)4O(OH)4·6H2O
Approval history:
Redefined formula IMA 21-D: Miyawaki et al. (2021), Vrtiška et al. (2022).
Classification of Beraunite
8.DC.27
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
C : With only medium-sized cations, (OH, etc.):RO4 = 1:1 and < 2:1
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
C : With only medium-sized cations, (OH, etc.):RO4 = 1:1 and < 2:1
42.11.16.1
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
11 : (AB)3(XO4)2Zq·xH2O
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
11 : (AB)3(XO4)2Zq·xH2O
19.13.10
19 : Phosphates
13 : Phosphates of Fe alone
19 : Phosphates
13 : Phosphates 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 for Standard |
|---|---|---|
| Bru | 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 Beraunite
Resinous, Pearly
Transparency:
Translucent
Comment:
Lustre pearly on cleavages, resinous on fractures.
Colour:
Dark red, reddish, brown-red
Streak:
Olive drab (unoxidized)
Hardness:
3 - 4 on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {100}
Good on {100}
Fracture:
Irregular/Uneven, Splintery
Density:
2.8 - 3.08 g/cm3 (Measured) 2.894 g/cm3 (Calculated)
Comment:
Calculated density value of 2.894 = greenish black material
Optical Data of Beraunite
Type:
Biaxial (+)
RI values:
nα = 1.707 - 1.775 nβ = 1.735 - 1.786 nγ = 1.738 - 1.820
2V:
Measured: 30° to 60°, Calculated: 66°
Birefringence:
0.031
Max. Birefringence:
δ = 0.031 - 0.045
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. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
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. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
relatively weak
Optical Extinction:
Y^c = 1.5-5°, Z = b (unoxidized)
Pleochroism:
Visible
Comments:
Colors depend on state of oxidation; The low RI represents beraunite (redefined as mixed valence iron phosphate). Oxidation results in higher refractive indices and approach the original eleonorite.
Chemistry of Beraunite
Mindat Formula:
Fe3+6(PO4)4O(OH)4 · 6H2O
Element Weights:
Elements listed:
Crystallography of Beraunite
Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Space Group:
Bb
Setting:
Cc
Cell Parameters:
a = 20.653(2) Å, b = 5.1433(6) Å, c = 19.241(2) Å
β = 93.56(9)°
β = 93.56(9)°
Ratio:
a:b:c = 4.016 : 1 : 3.741
Unit Cell V:
2,039.92 ų (Calculated from Unit Cell)
Morphology:
Crystals rare and small, tabular {100}, elongated [010], striated on {100} parallel to [010]. Coarse radial-fibrous aggregates; globular; discoidal with a coarse-fibrous structure; as crusts.
Twinning:
On {100}, may be interpenetrant.
Comment:
Space group Cc determined by Vrtiška et al. (2022); previously assumed to be C2/c. Cell-parameter values for restudied type material (Vrtiška et al., 2022). Data for orange material: a = 20.646, b = 5.129, c = 19.212 Å, β = 93.67°. Greenish black material (probably ferroberaunite) has: a = 20.953(8), b = 5.171(1), c = 19.266(4) Å, β = 93.34°.
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) |
|---|---|---|---|---|---|---|---|
| 0019158 | Beraunite | Moore P B, Kampf A R (1992) Beraunite: Refinement, comparative crystal chemistry, and selected bond valences Zeitschrift fur Kristallographie 201 263-281 |  | 1992 | Campanian age marls of Mullica Hill, New Jersey, USA | 0 | 293 |
| 0005231 | Beraunite | Marzoni Fecia di Cossato Y, Orlandi P, Pasero M (1989) Manganese-bearing beraunite from Mangualde, Portugal: mineral data and structure refinement The Canadian Mineralogist 27 441-446 | | 1989 | Mangualde, Portugal | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 10.37 Å | (100) |
| 9.58 Å | (50) |
| 7.229 Å | (50) |
| 5.18 Å | (10) |
| 4.825 Å | (60) |
| 4.418 Å | (50) |
| 4.09 Å | (20) |
| 3.747 Å | (30) |
| 3.47 Å | (30) |
| 3.33 Å | (10) |
| 3.187 Å | (40) |
| 3.082 Å | (60) |
| 2.838 Å | (20) |
| 2.732 Å | (30) |
| 2.705 Å | (30) |
| 2.582 Å | (30) |
| 2.488 Å | (20) |
| 2.422 Å | (20) |
| 2.312 Å | (25) |
| 2.227 Å | (20) |
| 2.154 Å | (10) |
| 2.109 Å | (30) |
| 2.082 Å | (10) |
| 2.058 Å | (10) |
| 2.009 Å | (30) |
| 1.972 Å | (10) |
| 1.923 Å | (30) |
| 1.870 Å | (10) |
| 1.830 Å | (10) |
| 1.813 Å | (10) |
| 1.764 Å | (10) |
| 1.767 Å | (10) |
| 1.742 Å | (10) |
| 1.718 Å | (20) |
| 1.691 Å | (15) |
| 1.662 Å | (10) |
| 1.641 Å | (10) |
| 1.621 Å | (30) |
| 1.599 Å | (10) |
| 1.570 Å | (10) |
| 1.541 Å | (20) |
| 1.459 Å | (20) |
| 1.436 Å | (20) |
| 1.372 Å | (10) |
| 1.328 Å | (10) |
| 1.315 Å | (10) |
| 1.290 Å | (20) |
| 1.279 Å | (20) |
| 1.240 Å | (10) |
Comments:
ICDD 22-631 See also ferroberaunite, the unoxidized end-member from Palermo #1 Quarry, Groton, NH, USA
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Geological Setting:
Bog iron ores, alteration of triphyllite in granitic pegmatites.
Type Occurrence of Beraunite
General Appearance of Type Material:
Dark red to orange crystals
Place of Conservation of Type Material:
Freiberg Mining Academy, Freiberg, Saxony, Germany: #21359.
Synonyms of Beraunite
Other Language Names for Beraunite
Relationship of Beraunite to other Species
Member of:
Other Members of Beraunite Group:
| Ferroberaunite | Fe2+Fe3+5(PO4)4(OH)5 · 6H2O | Mon. 2/m : B2/b |
| Tvrdýite | Fe2+Fe3+2Al3(PO4)4(OH)5(H2O)4 · 2H2O | Mon. 2/m : B2/b |
| Zincoberaunite | ZnFe3+5(PO4)4(OH)5 · 6H2O | Mon. 2/m : B2/b |
Common Associates
Associations Based on Photo Data:
| 262 photos of Beraunite associated with Strengite | FePO4 · 2H2O |
| 242 photos of Beraunite associated with Cacoxenite | Fe3+24AlO6(PO4)17(OH)12 · 75H2O |
| 119 photos of Beraunite associated with Kidwellite | NaFe3+9+x(PO4)6(OH)11 · 3H2O, x = 0.33 |
| 79 photos of Beraunite associated with Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe3+3(PO4)3(OH)5 |
| 56 photos of Beraunite associated with Strunzite | Mn2+Fe3+2(PO4)2(OH)2 · 6H2O |
| 43 photos of Beraunite associated with Dufrénite | Ca0.5Fe2+Fe3+5(PO4)4(OH)6 · 2H2O |
| 42 photos of Beraunite associated with |
Gutglück Mine, Braunfels, Lahn-Dill-Kreis, Giessen Region, Hesse, Germany