Boracite
A valid IMA mineral species - grandfathered
This page kindly sponsored by Alfredo Petrov
About Boracite
Formula:
Mg3(B7O13)Cl
Colour:
Green, blue, colourless, grey, white; dark green (ferroan); colourless in transmitted light
Lustre:
Adamantine, Vitreous
Hardness:
7 - 7½
Specific Gravity:
2.91 - 3.1
Crystal System:
Orthorhombic
Member of:
Name:
Named in allusion to the composition, containing BORon.
Dimorph of:
Boracite Group. Boracite-Ericaite Series. The magnesium analogue of Ericaite and Chambersite. The orthorhombic dimorph of Trembathite.
Boracite is found in evaporite deposits, usually associated with gypsum, anhydrite and/or halite.
Visit gemdat.org for gemological information about Boracite.
Boracite is found in evaporite deposits, usually associated with gypsum, anhydrite and/or halite.
Visit gemdat.org for gemological information about Boracite.Unique Identifiers
Mindat ID:
721
Long-form identifier:
mindat:1:1:721:2
Similar Names
| Barićite | A valid IMA mineral species | (Mg,Fe)3(PO4)2 · 8H2O |
| Beresite | A rock classification type | |
| Borcarite | A valid IMA mineral species | Ca4Mg(B4O6(OH)6)(CO3)2 |
| Brassite | A valid IMA mineral species | Mg(HAsO4) · 4H2O |
| Brosite | A synonym of 'Brossite' | |
| Brucite | A valid IMA mineral species - grandfathered | Mg(OH)2 |
| Brucite (of Dufrénoy) | A synonym of Zincite | |
| Brucite (of Gibbs) | A synonym of Chondrodite | |
| Bursaite | A discredited species name | Pb5Bi4S11 (?) |
| Coracite | A variety of 'Gummite' |
IMA Classification of Boracite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Mg3B7O13Cl
Classification of Boracite
6.GA.05
6 : BORATES
G : Heptaborates and other megaborates
A : Tekto-heptaborates
6 : BORATES
G : Heptaborates and other megaborates
A : Tekto-heptaborates
Dana 7th ed.:
25.6.1.1
25.6.1.1
25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
10.1.5
10 : Borates with other anions
1 : Borates with halide
10 : Borates with other anions
1 : Borates with halide
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 |
|---|---|---|
| Boc | 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 Boracite
Adamantine, Vitreous
Transparency:
Transparent, Translucent
Colour:
Green, blue, colourless, grey, white; dark green (ferroan); colourless in transmitted light
Comment:
Very rarely pink, yellow.
Streak:
White
Hardness:
7 - 7½ on Mohs scale
Cleavage:
None Observed
Fracture:
Irregular/Uneven, Conchoidal
Density:
2.91 - 3.1 g/cm3 (Measured) 2.97 g/cm3 (Calculated)
Optical Data of Boracite
Type:
Biaxial (+)
RI values:
nα = 1.658 - 1.662 nβ = 1.662 - 1.667 nγ = 1.668 - 1.673
2V:
Measured: 82°
Max. Birefringence:
δ = 0.010 - 0.011
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:
weak
Chemistry of Boracite
Mindat Formula:
Mg3(B7O13)Cl
Element Weights:
Elements listed:
Common Impurities:
Fe(II)
Crystallography of Boracite
Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Pca21
Cell Parameters:
a = 8.577(6) Å, b = 8.553(8) Å, c = 12.09(1) Å
Ratio:
a:b:c = 1.003 : 1 : 1.414
Unit Cell V:
882.47 ų
Z:
4
Morphology:
Crystals usually isolated in matrix; less often in groups. Small individuals may project from the face-centers of larger single crystals. Often cubic; also dodecahedral, tetrahedral; pseudo-octahedral or cuboctahedral with {111} commonly larger and brighter than {111}. Fine granular, fibrous to plumose aggregates. NOTE: above 265° the crystal system is isometric-hex'tetrahedral - 43_m.
Twinning:
On {111} as penetration twins, rare.
Crystallographic forms of Boracite
Crystal Atlas:
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Boracite no.2 - {100} - Goldschmidt (1913-1926)
Boracite no.5 - {110} - Goldschmidt (1913-1926)
Boracite no.41 - {111} - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by
www.smorf.nl.
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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) |
|---|---|---|---|---|---|---|---|
| 0010744 | Boracite | Dowty E, Clark J R (1973) Crystal-structure refinements for orthorhombic boracite, Mg3B7O13Cl, and a trigonal, iron-rich analogue Zeitschrift fur Kristallographie 138 64-99 |  | 1973 | Solvayshall, Roschwitz, Germany | 0 | 293 |
| 0019539 | Boracite | Ito T, Morimoto N, Sadanaga R (1951) The crystal structure of boracite Acta Crystallographica 4 310-316 |  | 1951 | Stassfurt, Germany | 0 | 293 |
| 0018134 | Boracite | Mehmel M (1932) Kristallstrukturelle Untersuchungen an Borazit _cod_database_code 1011284 Fortschritte der Mineralogie 17 436-438 | 1932 | synthetic | 0 | 293 | |
| 0019540 | Boracite | Ito T, Morimoto N, Sadanaga R (1951) The crystal structure of boracite Acta Crystallographica 4 310-316 | | 1951 | Stassfurt, Germany | 0 | 573 |
| 0000382 | Boracite | Sueno S, Clark J R, Papike J J, Konnert J A (1973) Crystal-structure refinement of cubic boracite American Mineralogist 58 691-697 | | 1973 | Solvayshall, Roschwitz, Germany | 0 | 673 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.044 Å | (100) |
| 3.025 Å | (88) |
| 2.705 Å | (55) |
| 3.492 Å | (45) |
| 2.137 Å | (30) |
| 6.050 Å | (27) |
| 2.468 Å | (21) |
Comments:
England. Data from Burns (1995).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
Bedded sedimentary deposits of gypsum and anhydrite; salt deposits; potash deposits of the oceanic type.
Type Occurrence of Boracite
Place of Conservation of Type Material:
Mining academy of Freiberg 19324
Geological Setting of Type Material:
Saltdome caprock of gypsum and anhydrite.
Associated Minerals at Type Locality:
Synonyms of Boracite
Other Language Names for Boracite
Dutch:Boraciet
German:Boracit
b-Boracit
Borazit
Kubische Quarzkrystalle
Lüneburger Sedativ-Spath
Metaboracit
Parasit
Würfelstein
b-Boracit
Borazit
Kubische Quarzkrystalle
Lüneburger Sedativ-Spath
Metaboracit
Parasit
Würfelstein
Italian:Boracite
Polish:Boracyt
Russian:Борацит
Simplified Chinese:方硼石
Traditional Chinese:方硼石
Varieties of Boracite
| Bromboracit | Artificial Bromine analogue of Boracite |
| Iron-bearing Boracite | |
| Stassfurtite | A fibrous variety of Boracite from Stassfurt, Germany. |
Relationship of Boracite to other Species
Member of:
Other Members of Boracite Group:
| Chambersite | Mn2+3(B7O13)Cl | Orth. mm2 : Pca21 |
| Congolite | Fe2+3B7O13Cl | Trig. 3m : R3c |
| Ericaite | Fe2+3(B7O13)Cl | Orth. mm2 : Pca21 |
| Trembathite | Mg3B7O13Cl | Trig. 3m : R3c |
Forms a series with:
Common Associates
Associations Based on Photo Data:
| 97 photos of Boracite associated with Hilgardite | Ca2B5O9Cl · H2O |
| 30 photos of Boracite associated with Anhydrite | CaSO4 |
| 7 photos of Boracite associated with Pyrite | FeS2 |
| 4 photos of Boracite associated with 'Hilgardite-3Tc' | Ca2B5O9Cl · H2O |
| 3 photos of Boracite associated with Chromite | Fe2+Cr3+2O4 |
| 3 photos of Boracite associated with Magnesite | MgCO3 |
| 2 photos of Boracite associated with Ericaite | Fe2+3(B7O13)Cl |
| 2 photos of Boracite associated with Gypsum | CaSO4 · 2H2O |
| 2 photos of Boracite associated with Halite | NaCl |
| 1 photo of Boracite associated with Preobrazhenskite | Mg3B11O15(OH)9 |
Related Minerals - Strunz-mindat Grouping
| 6.GA.05 | Ericaite | Fe2+3(B7O13)Cl |
| 6.GA.05 | Chambersite | Mn2+3(B7O13)Cl |
| 6.GA.10 | Congolite | Fe2+3B7O13Cl |
| 6.GA.10 | Trembathite | Mg3B7O13Cl |
| 6.GA.30 | Korzhinskite | Ca(B2O4) · H2O |
Other Information
Electrical:
Strongly piezoelectric and pyroelectric.
Thermal Behaviour:
Pyroelectric. At 265° the crystal system reverts to a high-temperature phase and the material becomes isotropic.
Notes:
Slowly but completely soluble in HCl. Very slowly decomposed by water.
Forms pseudomorphs after quartz (Douglashall).
Forms pseudomorphs after quartz (Douglashall).
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 Boracite
mindat.org URL:
https://www.mindat.org/min-721.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Boracite
Reference List:
Haüy, René Just (1822) Traité de Minéralogie (2nd ed.) Vol. 2. Bachelier, Paris. p.56 - Magnésie boratée
Dana, James D., Brush, George Jarvis (1868) A System of Mineralogy (5th ed.). p.882pages 596, 799 (as Huyssenite, Iron-boracite)
Gramont, Arnaud de (1890) Production artificielle de la boracite par voie humide. Bulletin de Minéralogie, 13 (7) 252-255 doi:10.3406/bulmi.1890.2181
Bøggild, Ο. B. (1912) Krystallform und Zwillingsbildungen des Kryoliths, des Perowskits und des Boracits. Zeitschrift für Kristallographie, 50 (1-6). 349-429 doi:10.1524/zkri.1912.50.1.349
Mehmel (1934) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 87: 239.(as Alpha-boracite)
Mehmel (1934) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 88: 1.(as Beta-boracite)
Guppy, E. M. (1944) Boracite from a boring at Aislaby, Yorkshire. Mineralogical Magazine and Journal of the Mineralogical Society, 27 (187) 51-53 doi:10.1180/minmag.1944.027.187.01
Dowty, Eric; Clark, Joan E. (1973) Crystal-structure refinements for orthorhombic boracite, Mg3ClB7O13, and a trigonal, iron-rich analogue. Zeitschrift für Kristallographie, 138 (1-4). 64-99 doi:10.1524/zkri.1973.138.1-4.64
Localities for Boracite
Showing 86 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.
Afghanistan | |
| Tucker et al. (2012) |
Australia | |
| Bottrill |
Bolivia | |
| Wilson (2001) |
| - (unpublished thesis) |
| Petrov (n.d.) |
| Federico Ahlfeld and Alfredo Petrov ... |
Canada | |
| Grice et al. (1996) +2 other references |
| Anderle et al. (1979) |
| Grice et al. (2005) |
| Boehner (1986) |
Chile | |
| Lohmeier et al. (2025) |
China | |
| She et al. (2022) |
| Xiao et al. (2022) |
| Liu et al. (2025) +1 other reference |
| Li et al. (2024) |
| Niu et al. (2024) |
| Jiang et al. (2025) |
| Xiaosong Xu and Jialing Wu (1983) +1 other reference |
Egypt | |
| Saleh et al. (2026) |
France | |
| Palache et al. (1951) |
Germany | |
| Weiß (1990) |
| Braitsch (1961) |
| |
| Weiß (1990) |
| Palache et al. (1951) |
| Weiß (1990) |
| Gerstenberg (n.d.) |
| Emser Hefte 1990 (1) |
| Palache et al. (1951) |
| Aufschluss 1987 (4) |
| Lavinsky (n.d.) |
| Hoffmann (1789) +3 other references |
| Palache et al. (1951) | |
| www.mineralienatlas.de (n.d.) |
| Mineralogical Society of America - ... |
| Wand et al. (1989) +3 other references |
| Feit (1889) +1 other reference |
| Palache et al. (1951) +1 other reference |
| Günther (1999) | |
| [var: Stassfurtite] ... |
| Naumann +1 other reference | |
| Palache et al. (1951) | |
| Brockt et al. (2001) |
| Mineralogical Society of America - ... |
| Naumann +1 other reference | |
| ... | |
| Palache et al. (1951) +1 other reference |
| Zeitschrift fUr Kristallographie et al. (1973) +1 other reference |
| Christian Bracke and M. Kampf specimens |
| Effmert +1 other reference |
| Heide et al. (1964) |
Kazakhstan | |
| Pekov et al. (1993) +2 other references |
| Box et al. (2012) |
| Mineralogical Society of America - ... +2 other references |
| Handbook of Mineralogy Vol V p 6 +5 other references |
Laos | |
| GAO et al. (2012) |
Pacific Ocean | |
| Choi et al. (2026) |
Poland | |
| Jirásek +8 other references |
| Praszkier (2010) |
| Wachowiak et al. (2012) |
| Kucha (1979) +1 other reference |
Republic of the Congo | |
| Henry Rauche (2009) |
Russia | |
| Vladykin et al. (2017) |
| Pekov et al. (2001) +2 other references |
| Mazurov et al. (2007) |
South Africa | |
| Rozendaa et al. (2012) |
South Georgia and the South Sandwich Islands | |
| Baker (1978) | |
Thailand | |
| Suwanich (2010) |
UK | |
| [var: Iron-bearing Boracite] BMS Collection +3 other references |
| Palache et al. (1951) |
| Smith et al. (2014) |
| Smith et al. (2014) | |
| Kemp et al. (2016) | |
USA | |
| Mineralogical Society of America - ... |
| Rocks & Min.: 64:472. +1 other reference | |
| Justin Zzyzx specimen |
| Error in 1930s State publication |
| Smith (1994) |
| Hurlbut et al. (1937) +1 other reference |
| Smith (1994) |
| R&M 69:3 pp 156-162 | |
| Smith (1994) | |
| Van Rythoven et al. (2020) |
| Hutchinson et al. (2022) |
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Lüneburger Kalkberg, Lüneburg, Lüneburg District, Lower Saxony, Germany