Borcarite
A valid IMA mineral species
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About Borcarite
Formula:
Ca4Mg(B4O6(OH)6)(CO3)2
Colour:
Greenish-blue to bluish green, nearly colorless, colorless in section
Lustre:
Vitreous, Pearly
Hardness:
4
Specific Gravity:
2.77
Crystal System:
Monoclinic
Name:
Named in allusion to its composition, being a BORate and CARbonate.
This page provides mineralogical data about Borcarite.
Unique Identifiers
Mindat ID:
723
Long-form identifier:
mindat:1:1:723:0
Similar Names
| Boracite | A valid IMA mineral species - grandfathered | Mg3(B7O13)Cl |
IMA Classification of Borcarite
Approved
IMA Formula:
Ca4MgB4O6(CO3)2(OH)6
First published:
1965
Classification of Borcarite
6.DA.40
6 : BORATES
D : Tetraborates
A : Neso-tetraborates
6 : BORATES
D : Tetraborates
A : Neso-tetraborates
27.1.3.1
27 : COMPOUND BORATES
1 : Miscellaneous
27 : COMPOUND BORATES
1 : Miscellaneous
10.4.3
10 : Borates with other anions
4 : Borates with carbonate
10 : Borates with other anions
4 : Borates with carbonate
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 |
|---|---|---|
| Bcr | 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 Borcarite
Vitreous, Pearly
Transparency:
Translucent
Comment:
slightly pearly on cleavages.
Colour:
Greenish-blue to bluish green, nearly colorless, colorless in section
Hardness:
4 on Mohs scale
Cleavage:
Perfect
Perfect on {100} and {110} and in several directions {hkl} and {hOl} with angles β 50-70°. The cleavage plane {100} is always smooth; the cleavage plane {110} is very often striated parallel to c.
Perfect on {100} and {110} and in several directions {hkl} and {hOl} with angles β 50-70°. The cleavage plane {100} is always smooth; the cleavage plane {110} is very often striated parallel to c.
Density:
2.77(1) g/cm3 (Measured) 2.765 g/cm3 (Calculated)
Optical Data of Borcarite
Type:
Biaxial (-)
RI values:
nα = 1.59 nβ = 1.651 nγ = 1.657
2V:
Measured: 30° (2), Calculated: 32°
Max. Birefringence:
δ = 0.067
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:
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:
r < v distinct
Comments:
Z = b; Y ∧ c = 28(4)°
Chemistry of Borcarite
Mindat Formula:
Ca4Mg(B4O6(OH)6)(CO3)2
Element Weights:
Crystallography of Borcarite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 17.840(4) Å, b = 8.380(2) Å, c = 4.445(1) Å
β = 102.04(3)°
β = 102.04(3)°
Ratio:
a:b:c = 2.129 : 1 : 0.53
Unit Cell V:
649.91 ų (Calculated from Unit Cell)
Z:
2
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Display Options
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Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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View
CIF File Best | x | y | z | a | b | c
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Rotation
Stop | Start
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Labels
Console Off | On | Grey | Yellow
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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) |
|---|---|---|---|---|---|---|---|
| 0014516 | Borcarite | Burns P C, Hawthorne F C (1995) Hydrogen bonding in borcarite, an unusual borate-carbonate mineral Mineralogical Magazine 59 297-304 |  | 1995 | Yakutskaya, Russia | 0 | 293 |
| 0020477 | Borcarite | Yamnova N A, Simonov M A, Kazanskaya E V, Belov N V (1975) Refinement of the crystal structure of the Ca, Mg-carbonatoborate borcarite Ca4Mg/B4O6(OH)6/(CO3)2 Soviet Physics Doklady 20 799-801 | 1975 | Solongo metasomatite deposit, Buryatia, Russia | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.57 Å | (100) |
| 2.67 Å | (100) |
| 1.886 Å | (100) |
| 2.91 Å | (90) |
| 2.27 Å | (90) |
| 2.21 Å | (90) |
| 1.610 Å | (90) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 31 : Thermally altered carbonate, phosphate, and iron formations | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Type Occurrence of Borcarite
General Appearance of Type Material:
Dense masses up to 0.5 m in diameter and as veins.
Place of Conservation of Type Material:
1) Vernadsky Geological Museum, Moscow, Russia, 48151.
2) A.E. Fersman Mineralogical Museum, Academy of Sciences, Moscow, Russia, 68747, 68748.
2) A.E. Fersman Mineralogical Museum, Academy of Sciences, Moscow, Russia, 68747, 68748.
Geological Setting of Type Material:
Occurs in kotoite marbles, formed in dolomites near a contact with granodiorite.
Associated Minerals at Type Locality:
Other Language Names for Borcarite
Common Associates
Associations Based on Photo Data:
| 75 photos of Borcarite associated with Cahnite | Ca2[B(OH)4](AsO4) |
| 7 photos of Borcarite associated with Numanoite | Ca4Cu(B4O6(OH)6)(CO3)2 |
| 6 photos of Borcarite associated with Szaibélyite | MgBO2(OH) |
| 4 photos of Borcarite associated with Nifontovite | Ca3B6O6(OH)12(H2O)2 |
| 1 photo of Borcarite associated with Fedorovskite | Ca2Mg2B4O7(OH)6 |
| 1 photo of Borcarite associated with Roweite | Ca2Mn2+2B4O7(OH)6 |
| 1 photo of Borcarite associated with Calcite | CaCO3 |
| 1 photo of Borcarite associated with Quartz | SiO2 |
| 1 photo of Borcarite associated with Ludwigite | Mg2Fe3+(BO3)O2 |
Related Minerals - Strunz-mindat Grouping
| 6.DA.10 | Borax | Na2(B4O5)(OH)4 · 8H2O |
| 6.DA.15 | Tincalconite | Na2(B4O7) · 5H2O |
| 6.DA.20 | Hungchaoite | Mg(B4O7) · 9H2O |
| 6.DA.25 | Roweite | Ca2Mn2+2B4O7(OH)6 |
| 6.DA.25 | Fedorovskite | Ca2Mg2B4O7(OH)6 |
| 6.DA.30 | Hydrochlorborite | Ca4B8O15Cl2 · 21H2O |
| 6.DA.35 | Uralborite | Ca2[B3O3(OH)5 · OB(OH)3] |
| 6.DA.40 | Numanoite | Ca4Cu(B4O6(OH)6)(CO3)2 |
| 6.DA.60 | Fontarnauite | (Na,K)2(Sr,Ca)(SO4)[B5O8(OH)] · 2H2O |
Other Information
Notes:
Not soluble in water. Easily soluble in acids, even acetic. Effervesces in HCl.
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 Borcarite
mindat.org URL:
https://www.mindat.org/min-723.html
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Please feel free to link to this page.
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References for Borcarite
Reference List:
Burns, P. C., Hawthorne, F. C. (1995) Hydrogen bonding in borcarite, an unusual borate-carbonate mineral. Mineralogical Magazine, 59 (395) 297-304 doi:10.1180/minmag.1995.059.395.13
Localities for Borcarite
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.
China | |
| Ottens et al. (2012) |
| Ottens et al. (2014) | |
Japan | |
| Kusachi et al. (1997) +2 other references |
Mexico | |
| Peter Megaw collection |
| Carnegie Museum of Natural History ... | |
| Natural History Museum Vienna collection (specimen bought from Jaroslav Hyršl in Nov. 2025) | |
Pakistan | |
| Bashir et al. (2009) |
Russia | |
| Handbook of Mineralogy. +1 other reference |
| Pertzev et al. (1965) +2 other references |
| Jeff Weissman collection |
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Charcas, Charcas Municipality, San Luis Potosí, Mexico