Boralsilite
A valid IMA mineral species
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About Boralsilite
Formula:
Al16B6O30(Si2O7)
Colour:
Colorless
Lustre:
Vitreous
Specific Gravity:
3.07 (Calculated)
Crystal System:
Monoclinic
Name:
Named after its composition, containing BORon, ALuminum, and SILicon.
First anhydrous Al-B-silicate to be discovered in nature. At Stornes Peninsula the borasilite may be partly replaced by diaspore.
Unique Identifiers
Mindat ID:
6829
Long-form identifier:
mindat:1:1:6829:7
GUID
(UUID V4):
(UUID V4):
5b7e17dc-f1ab-4f9b-9d3e-cb13a136af98
IMA Classification of Boralsilite
Approved
First published:
1998
Type description reference:
Grew, Edward S., McGee, James J., Yates, Martin G., Peacor, Donald R., Rouse, Roland C., Huijsmanns, Joep P. P., Shearer, Charles K., Wiedenbeck, Michael, Thost, Douglas E., Su, Shu-Chun (1998) Boralsilite (Al16B6Si2O37); a new mineral related to sillimanite from pegmatites in granulite-facies rocks. American Mineralogist, 83 (5) 638-651 doi:10.2138/am-1998-5-624
Classification of Boralsilite
9.BD.30
9 : SILICATES (Germanates)
B : Sorosilicates
D : Si2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination
9 : SILICATES (Germanates)
B : Sorosilicates
D : Si2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination
Mineral Symbols
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.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Symbol | Source | Reference |
---|---|---|
Bor | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Bor | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of Boralsilite
Vitreous
Transparency:
Translucent
Colour:
Colorless
Streak:
White
Hardness Data:
Could not be measured
Comment:
Hardness could not be accurately determined because of the small crystal size and common alteration.
Density:
3.07 g/cm3 (Calculated)
Optical Data of Boralsilite
Type:
Biaxial (+)
RI values:
nα = 1.629(1) nβ = 1.640(1) nγ = 1.654(1)
2V:
Measured: 81.8° (6), Calculated: 84°
Max Birefringence:
δ = 0.025
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
Very weak, r > v.
Optical Extinction:
Y = b. Positive elongation.
Chemistry of Boralsilite
Mindat Formula:
Al16B6O30(Si2O7)
Elements listed:
Crystallography of Boralsilite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 14.767 Å, b = 5.574 Å, c = 15.079 Å
β = 91.96°
β = 91.96°
Ratio:
a:b:c = 2.649 : 1 : 2.705
Unit Cell V:
1,240.45 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Prisms in open clusters or tight bundles up to 1 cm long.
Twinning:
Commonly twinned. Near-universal presence of fine twinning on {100}, which is not always evident optically.
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) |
---|---|---|---|---|---|---|---|
0002272 | Boralsilite | Peacor D R, Rouse R C, Grew E S (1999) The crystal structure of boralsilite and its relation to a family of boroaluminosilicates, sillimanite, and andalusite American Mineralogist 84 1152-1161 | 1999 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
d-spacing | Intensity |
---|---|
5.19 Å | (100) |
5.41 Å | (70) |
4.31 Å | (70) |
4.95 Å | (60) |
3.378 Å | (60) |
2.162 Å | (40) |
3.59 Å | (30) |
Comments:
Larsemann Hills, Prydz Bay, Antarctica. Data are from the type description.
Geological Environment
Paragenetic Mode(s):
Paragenetic Mode | Earliest Age (Ga) |
---|---|
Stage 4a: Earth’s earliest continental crust | >4.4-3.0 |
19 : Granitic intrusive rocks |
Type Occurrence of Boralsilite
Co-Type Localities:
General Appearance of Type Material:
Forms a single patch of fibrous aggregates of fine prisms in a quartz rich part of the specimen (Larsemanns Hills).
Place of Conservation of Type Material:
In the National Museum of Natural History, Smithsonian Institution as NMNH 171403 and the Almgjotheii specimen as NMNH 171404.
Chemical Analysis of Type Material:
SiO2 | 12.67 % |
---|---|
MgO | 0.23 % |
FeO | 1.10 % |
Al2O3 | 69.15 % |
B2O3 | 16.775 % |
BeO | 0.094 % |
Total: | 100.019 % |
Geological Setting of Type Material:
Pegmatites cutting granulite-facies metapelitic rocks.
Associated Minerals at Type Locality:
Reference:
Grew, E.S., McGee, J.J., Yates, M.G., Peacor, D.R., Rouse, R.C., Huijsmans, J.P.P., Shearer, C.K., Wiedenbeck, M., Thost, D.E., and Su, S.-C. (1998): Boralsilite (Al16B6Si2O37): A new mineral related to sillimanite from pegmatites in granulite-facies rocks. American Mineralogist: 83: 638-651
Synonyms of Boralsilite
Other Language Names for Boralsilite
Common Associates
Associated Minerals Based on Photo Data:
4 photos of Boralsilite associated with Tourmaline | AD3G6 (T6O18)(BO3)3X3Z |
Related Minerals - Strunz-mindat Grouping
9.BD.05 | Bertrandite | Be4(Si2O7)(OH)2 |
9.BD.10 | Hemimorphite | Zn4Si2O7(OH)2 · H2O |
9.BD.15 | Junitoite | CaZn2Si2O7 · H2O |
9.BD.20 | Axinite-(Fe) | Ca2Fe2+Al2BSi4O15OH |
9.BD.20 | Axinite-(Mg) | Ca2MgAl2BSi4O15OH |
9.BD.20 | Axinite-(Mn) | Ca2Mn2+Al2BSi4O15(OH) |
9.BD.20 | Tinzenite | Ca2Mn2+4Al4[B2Si8O30](OH)2 |
9.BD.25 | Vistepite | SnMn4B2Si4O16(OH)2 |
9.BD.35 | Werdingite | (Mg,Fe)2Al14Si4B4O37 |
9.BD.40 | Vránaite | Al16B4Si4O38 |
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 Boralsilite
mindat.org URL:
https://www.mindat.org/min-6829.html
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References for Boralsilite
Reference List:
Grew, Edward S., McGee, James J., Yates, Martin G., Peacor, Donald R., Rouse, Roland C., Huijsmanns, Joep P. P., Shearer, Charles K., Wiedenbeck, Michael, Thost, Douglas E., Su, Shu-Chun (1998) Boralsilite (Al16B6Si2O37); a new mineral related to sillimanite from pegmatites in granulite-facies rocks. American Mineralogist, 83 (5) 638-651 doi:10.2138/am-1998-5-624
Localities for Boralsilite
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).
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.
All localities listed without proper references should be considered as questionable.
Antarctica | |
| Wadoski et al. (2011) +1 other reference |
| Grew et al. (1998) |
Czech Republic | |
| CEMPÍREK |
Madagascar | |
| Novák et al. (2015) |
Norway (TL) | |
| Grew (1998) +1 other reference |
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Stornes Peninsula, Larsemann Hills, Prydz Bay, Ingrid Christensen Coast, Princess Elizabeth Land, Eastern Antarctica, Antarctica