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Embreyite
A valid IMA mineral species
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About Embreyite
Peter Embrey
Formula:
Pb5(CrO4)2(PO4)2 · H2O
Colour:
Dull orange
Lustre:
Resinous, Dull
Hardness:
3½
Specific Gravity:
6.45
Crystal System:
Monoclinic
Name:
Named in honor of Peter Godwin Embrey (1929-2010), British Museum. His achievements in the science included the reprint of Greg and Lettsom's British Mineralogy in 1977, and Minerals of Cornwall and Devon published in 1987.
See also https://www.mindat.org/mesg-631485.html for more info on Peter Embrey.
See also https://www.mindat.org/mesg-631485.html for more info on Peter Embrey.
Type Locality:
Unique Identifiers
Mindat ID:
1373
Long-form identifier:
mindat:1:1:1373:0
IMA Classification of Embreyite
Approved
IMA Formula:
Pb2+5(Cr6+O4)2(PO4)2·H2O
Approval year:
1971
First published:
1972
Classification of Embreyite
7.FC.20
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
C : With PO4, AsO4, SiO4
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
C : With PO4, AsO4, SiO4
43.3.2.1
43 : COMPOUND PHOSPHATES, ETC.
3 : Hydrated Normal Compound Phosphates, etc·
43 : COMPOUND PHOSPHATES, ETC.
3 : Hydrated Normal Compound Phosphates, etc·
22.5.2
22 : Phosphates, Arsenates or Vanadates with other Anions
5 : Phosphates, arsenates or vanadates with chromate, molybdate, niobate or tantalate
22 : Phosphates, Arsenates or Vanadates with other Anions
5 : Phosphates, arsenates or vanadates with chromate, molybdate, niobate or tantalate
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 |
|---|---|---|
| Emb | 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 Embreyite
Resinous, Dull
Transparency:
Transparent, Translucent
Comment:
Dull to resinous
Colour:
Dull orange
Comment:
Various shades of orange.
Streak:
Yellow
Hardness:
3½ on Mohs scale
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Irregular/Uneven
Density:
6.45(12) g/cm3 (Measured) 6.564 g/cm3 (Calculated)
Optical Data of Embreyite
Type:
Biaxial (-)
RI values:
nα = 2.2 nβ = 2.36 nγ = 2.36
Max. Birefringence:
δ = 0.160
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.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
relatively strong
Optical Extinction:
Y = b.
Pleochroism:
Weak
Comments:
X = honey-yellow; Y = Z = amber.
Chemistry of Embreyite
Mindat Formula:
Pb5(CrO4)2(PO4)2 · H2O
Element Weights:
Crystallography of Embreyite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 9.802(16) Å, b = 5.603(9) Å, c = 7.649(12) Å
β = 114.85°
β = 114.85°
Ratio:
a:b:c = 1.749 : 1 : 1.365
Unit Cell V:
381.2 ų
Z:
1
Twinning:
Multiple twinning and 60° sector zoning observed optically.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.167 Å | (100) |
| 4.751 Å | (60) |
| 2.818 Å | (60) |
| 1.917 Å | (45) |
| 3.563 Å | (32) |
| 2.213 Å | (32) |
| 2.187 Å | (31) |
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] | |
| 47e : [Vanadates, chromates, manganates] |
Type Occurrence of Embreyite
General Appearance of Type Material:
Thick botryoidal crusts consisting of tiny tabular crystals with the plane of flattening approximately normal to the surface of the crust.
Place of Conservation of Type Material:
The Natural History Museum, London, England, number 39316.
Associated Minerals at Type Locality:
Synonyms of Embreyite
Other Language Names for Embreyite
Common Associates
Associations Based on Photo Data:
| 30 photos of Embreyite associated with Pyromorphite | Pb5(PO4)3Cl |
| 26 photos of Embreyite associated with Crocoite | PbCr6+O4 |
| 15 photos of Embreyite associated with Vauquelinite | Pb2Cu(CrO4)(PO4)(OH) |
| 2 photos of Embreyite associated with Trippkeite | Cu2+As3+2O4 |
| 2 photos of Embreyite associated with Mimetite | Pb5(AsO4)3Cl |
| 1 photo of Embreyite associated with Quartz | SiO2 |
| 1 photo of Embreyite associated with Bindheimite | Pb2Sb2O6O |
| 1 photo of Embreyite associated with Chrysocolla | Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O, x < 1 |
| 1 photo of Embreyite associated with Shattuckite | Cu5(Si2O6)2(OH)2 |
| 1 photo of Embreyite associated with Cerussite | PbCO3 |
Related Minerals - Strunz-mindat Grouping
| 7.FC.05 | Vauquelinite | Pb2Cu(CrO4)(PO4)(OH) |
| 7.FC.10 | Fornacite | Pb2Cu(CrO4)(AsO4)(OH) |
| 7.FC.10 | Molybdofornacite | Pb2Cu(MoO4,CrO4)(AsO4,PO4)(OH) |
| 7.FC.15 | Hemihedrite | Pb10Zn(CrO4)6(SiO4)2(OH)2 |
| 7.FC.15 | Raygrantite | Pb10Zn(SO4)6(SiO4)2(OH)2 |
| 7.FC.15 | Iranite | Pb10Cu(CrO4)6(SiO4)2(OH)2 |
| 7.FC.20 | Cassedanneite | Pb5(CrO4)2(VO4)2 · H2O |
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 Embreyite
mindat.org URL:
https://www.mindat.org/min-1373.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 Embreyite
Localities for Embreyite
Showing 9 localities.
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.
France | |
| Cuchet et al. (2008) |
Germany | |
| Leonhardt et al. (1991) +1 other reference |
Russia | |
| Pekov et al. (2026) |
| Williams (1972) |
| Pavel M. Kartashov (n.d.) | |
South Africa | |
| Southwood et al. (1986) |
| Cairncross et al. (1995) | |
| SAMS (South African Micromount Society) |
USA | |
| Möckel (2018) |
Quick NavTopAbout EmbreyiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Callenberg, Zwickau District, Saxony, Germany