Pokrovskite
A valid IMA mineral species
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About Pokrovskite
Pavel V. Pokrovski
Formula:
Mg2(CO3)(OH)2
Colour:
Pinkish-white to tan
Lustre:
Dull
Hardness:
3
Specific Gravity:
2.51 - 2.52
Crystal System:
Monoclinic
Member of:
Name:
Named in honor of Pavel Vladimirovich Pokrovskii (Павел Владимирович Покровский) (19 May 1912, Rybinsk, Yaroslavl, Russian Empire – 2 August 1979, Sverdlovsk, Russia), mineralogist, Institute of Geology and Geochemistry, Sverdlovsk, Russia.
This page provides mineralogical data about Pokrovskite.
Unique Identifiers
Mindat ID:
3250
Long-form identifier:
mindat:1:1:3250:2
IMA Classification of Pokrovskite
Approved
IMA Formula:
Mg2CO3(OH)2
Approval year:
1982
Classification of Pokrovskite
5.BA.10
5 : CARBONATES (NITRATES)
B : Carbonates with additional anions, without H2O
A : With Cu, Co, Ni, Zn, Mg, Mn
5 : CARBONATES (NITRATES)
B : Carbonates with additional anions, without H2O
A : With Cu, Co, Ni, Zn, Mg, Mn
16a.3.1.5
16a : ANHYDROUS CARBONATES CONTAINING HYDROXYL OR HALOGEN
3 : (AB)2(XO3)Zq
16a : ANHYDROUS CARBONATES CONTAINING HYDROXYL OR HALOGEN
3 : (AB)2(XO3)Zq
11.3.5
11 : Carbonates
3 : Carbonates of Mg
11 : Carbonates
3 : Carbonates of Mg
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 |
|---|---|---|
| Pkr | 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 Pokrovskite
Dull
Transparency:
Translucent
Colour:
Pinkish-white to tan
Comment:
may be opaque due to inclusions.
Streak:
White
Hardness:
3 on Mohs scale
Density:
2.51 - 2.52 g/cm3 (Measured) 2.58 g/cm3 (Calculated)
Optical Data of Pokrovskite
Type:
Biaxial (-)
RI values:
nα = 1.537 nβ = 1.619 nγ = 1.619
2V:
Measured: 18° , Calculated: 34°
Max. Birefringence:
δ = 0.082
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:
Moderate (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:
weak
Chemistry of Pokrovskite
Mindat Formula:
Mg2(CO3)(OH)2
Element Weights:
Elements listed:
Crystallography of Pokrovskite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/a
Cell Parameters:
a = 9.43(1) Å, b = 12.27(1) Å, c = 3.395(3) Å
β = 96.60(9)°
β = 96.60(9)°
Ratio:
a:b:c = 0.769 : 1 : 0.277
Unit Cell V:
390.22 ų (Calculated from Unit Cell)
Z:
4
Comment:
by analogy to malachite
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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CIF File Best | x | y | z | a | b | c
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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) |
|---|---|---|---|---|---|---|---|
| 0007185 | Pokrovskite | Perchiazzi N, Merlino S (2006) The malachite-rosasite group: crystal structures of glaukosphaerite and pokrovskite European Journal of Mineralogy 18 787-792 | 2006 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.60 Å | (10b) |
| 2.17 Å | (9) |
| 6.10 Å | (7) |
| 4.70 Å | (7) |
| 3.73 Å | (7) |
| 1.661 Å | (7b) |
| 1.385 Å | (5) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 7 : Ultramafic igneous rocks |
Type Occurrence of Pokrovskite
Place of Conservation of Type Material:
A.E. Fersman Mineralogical Museum, Academy of Sciences, Moscow, Russia.
Associated Minerals at Type Locality:
Synonyms of Pokrovskite
Other Language Names for Pokrovskite
Relationship of Pokrovskite to other Species
Member of:
Other Members of Malachite-Rosasite Group:
| Chukanovite | Fe2+2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Glaukosphaerite | (Cu,Ni)2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Kolwezite | CuCo(CO3)(OH)2 | Tric. |
| Malachite | Cu2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Mcguinnessite | (Mg,Cu)2(CO3)(OH)2 | Mon. 2/m |
| Nullaginite | Ni2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Parádsasvárite | Zn2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Perchiazziite | Co2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Rosasite | (Cu,Zn)2(CO3)(OH)2 | Mon. 2/m : P21/b |
| Zincrosasite | (Zn,Cu)2(CO3)(OH)2 | Mon. |
Common Associates
Associations Based on Photo Data:
| 5 photos of Pokrovskite associated with Hydromagnesite | Mg5(CO3)4(OH)2 · 4H2O |
| 5 photos of Pokrovskite associated with 'Pyroaurite-2H' | Mg6Fe3+2(OH)16(CO3) · 4H2O |
| 5 photos of Pokrovskite associated with Magnesite | MgCO3 |
| 3 photos of Pokrovskite associated with Magnetite | Fe2+Fe3+2O4 |
| 3 photos of Pokrovskite associated with Serpentine Subgroup | D3[Si2O5](OH)4 |
| 3 photos of Pokrovskite associated with Mcguinnessite | (Mg,Cu)2(CO3)(OH)2 |
| 3 photos of Pokrovskite associated with Calcite | CaCO3 |
Related Minerals - Strunz-mindat Grouping
| 5.BA.05 | Azurite | Cu3(CO3)2(OH)2 |
| 5.BA.10 | Mcguinnessite | (Mg,Cu)2(CO3)(OH)2 |
| 5.BA.10 | Zincrosasite | (Zn,Cu)2(CO3)(OH)2 |
| 5.BA.10 | Parádsasvárite | Zn2(CO3)(OH)2 |
| 5.BA.10 | Rosasite | (Cu,Zn)2(CO3)(OH)2 |
| 5.BA.10 | Nullaginite | Ni2(CO3)(OH)2 |
| 5.BA.10 | Georgeite | [Cu(OH)2-x(H2O)x][CO3]x/2 |
| 5.BA.10 | Glaukosphaerite | (Cu,Ni)2(CO3)(OH)2 |
| 5.BA.10 | Kolwezite | CuCo(CO3)(OH)2 |
| 5.BA.10 | Chukanovite | Fe2+2(CO3)(OH)2 |
| 5.BA.10 | Malachite | Cu2(CO3)(OH)2 |
| 5.BA.10 | Perchiazziite | Co2(CO3)(OH)2 |
| 5.BA.15 | Aurichalcite | (Zn,Cu)5(CO3)2(OH)6 |
| 5.BA.15 | Hydrozincite | Zn5(CO3)2(OH)6 |
| 5.BA.20 | Holdawayite | Mn6(CO3)2(OH)7(Cl,OH) |
| 5.BA.25 | 'UM1977-03-COSiO:CaClH' | Ca10-11(CO3)7(SiO4)Cl1-2(OH)1-2 |
| 5.BA.25 | Defernite | Ca6(CO3)1.58(Si2O7)0.21(OH)7[Cl0.50(OH)0.08(H2O)0.42] |
| 5.BA.30 | Sclarite | Zn7(CO3)2(OH)10 |
| 5.BA.30 | Loseyite | (Mn2+,Zn,Mg)4Zn3(CO3)2(OH)10 |
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 Pokrovskite
mindat.org URL:
https://www.mindat.org/min-3250.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Pokrovskite
Reference List:
Dunn, Pete J., Chao, George Y., Fleischer, Michael, Ferraiolo, James A., Langley, Richard H., Pabst, Adolf, Zilczer, Janet A. (1985) New mineral names. American Mineralogist, 70 (1-2) 214-221 p.217
Perchiazzi, Natale; Merlino, Stefano (2006) The malachite-rosasite group: crystal structures of glaukosphaerite and pokrovskite. European Journal of Mineralogy, 18 (6). 787-792 doi:10.1127/0935-1221/2006/0018-0787
Frost, Ray L. (2006) A Raman spectroscopic study of selected minerals of the rosasite group. Journal of Raman Spectroscopy, 37 (9) 910-921 doi:10.1002/jrs.1521
Chaka, Anne M. (2016) Ab Initio Thermodynamics and the Relationship between Octahedral Distortion, Lattice Structure, and Proton Substitution Defects in Malachite/Rosasite Group Endmember Pokrovskite Mg2CO3(OH)2. The Journal of Physical Chemistry A, 120 (51). 10181-10195 doi:10.1021/acs.jpca.6b11969
Localities for Pokrovskite
Showing 10 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.
Germany | |
| Blaß et al. (1994) +1 other reference |
Japan | |
| Prof |
Kazakhstan (TL) | |
| Pekov (1998) |
USA | |
| G. C. Jones and B. Jackson (1993) |
| Frost (2006) |
| Parker (2005) |
| Castor et al. (2004) |
| Bernard et al. (2004) |
| FM newsletter vol.31 no.1 Jan-Mar '01 ... |
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Addie Quarry, Jackson County, North Carolina, USA