Hydroboracite
A valid IMA mineral species - grandfathered
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About Hydroboracite
Formula:
CaMg[B3O4(OH)3]2 · 3H2O
Colour:
Colourless, white
Lustre:
Vitreous, Silky
Hardness:
2 - 3
Specific Gravity:
2.15 - 2.17
Crystal System:
Monoclinic
Name:
In allusion to the composition, being a HYDRated BORAte.
This page provides mineralogical data about Hydroboracite.
Unique Identifiers
Mindat ID:
1967
Long-form identifier:
mindat:1:1:1967:1
IMA Classification of Hydroboracite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
CaMg[B3O4(OH)3]2·3H2O
Type description reference:
Classification of Hydroboracite
6.CB.15
6 : BORATES
C : Triborates
B : Ino-triborates
6 : BORATES
C : Triborates
B : Ino-triborates
26.3.6.1
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
3 : Triborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
3 : Triborates
9.3.22
9 : Borates
3 : Borates of Ca and Sr
9 : Borates
3 : Borates of Ca and Sr
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 |
|---|---|---|
| Hbo | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Hydroboracite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Hydroboracite
Vitreous, Silky
Transparency:
Transparent, Translucent
Comment:
silky if fibrous
Colour:
Colourless, white
Hardness:
2 - 3 on Mohs scale
Comment:
Hardness = 2–3; 5–6 in some specimens.
Cleavage:
Perfect
{010}, perfect; {100}, distinct.
{010}, perfect; {100}, distinct.
Density:
2.15 - 2.17 g/cm3 (Measured) 2.170 g/cm3 (Calculated)
Optical Data of Hydroboracite
Type:
Biaxial (+)
RI values:
nα = 1.520 - 1.523 nβ = 1.534 - 1.535 nγ = 1.569 - 1.571
2V:
Measured: 60° to 66°, Calculated: 62° to 66°
Max. Birefringence:
δ = 0.048 - 0.049
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:
None to Very Low
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:
relatively weak r < v
Chemistry of Hydroboracite
Mindat Formula:
CaMg[B3O4(OH)3]2 · 3H2O
Element Weights:
Crystallography of Hydroboracite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/b
Setting:
P112/b
Cell Parameters:
a = 11.769(2) Å, b = 6.684(2) Å, c = 8.235(4) Å
β = 102.59(2)°
β = 102.59(2)°
Ratio:
a:b:c = 1.761 : 1 : 1.232
Unit Cell V:
632.22 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals elongated [001] and flattened {010}. Lamellar-fibrous radiating or columnar. Compact and fine-grained.
Crystal Structure
Load
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) |
|---|---|---|---|---|---|---|---|
| 0005149 | Hydroboracite | Sabelli C, Stoppioni A (1978) Refinement of the crystal structure of hydroboracite The Canadian Mineralogist 16 75-80 |  | 1978 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.78 Å | (100) |
| 6.69 Å | (85) |
| 3.32 Å | (74) |
| 1.914 Å | (16) |
| 4.47 Å | (14) |
| 2.436 Å | (14) |
| 4.36 Å | (13) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Type Occurrence of Hydroboracite
Geological Setting of Type Material:
The original description of the type locality is the Caucasus. The original location has not been found.
Other Language Names for Hydroboracite
Dutch:Hydroboraciet
German:Hydroboracit
Russian:Гидроборацит
Simplified Chinese:水方硼石
Spanish:Hidroboracita
Traditional Chinese:水方硼石
Common Associates
Associations Based on Photo Data:
| 31 photos of Hydroboracite associated with Colemanite | Ca[B3O4(OH)3] · H2O |
| 11 photos of Hydroboracite associated with Anhydrite | CaSO4 |
| 8 photos of Hydroboracite associated with Tunellite | SrB6O9(OH)2 · 3H2O |
| 5 photos of Hydroboracite associated with Gypsum | CaSO4 · 2H2O |
| 2 photos of Hydroboracite associated with Celestine | SrSO4 |
| 1 photo of Hydroboracite associated with Szaibélyite | MgBO2(OH) |
| 1 photo of Hydroboracite associated with Görgeyite | K2Ca5(SO4)6 · H2O |
Related Minerals - Strunz-mindat Grouping
| 6.CB.10 | Colemanite | Ca[B3O4(OH)3] · H2O |
| 6.CB.20 | Howlite | Ca2B5SiO9(OH)5 |
| 6.CB.25 | Jarandolite | Ca[B3O4(OH)3] |
Other Information
IR Spectrum:
material from District #99 of an underground mine within the Inder deposit [cm-1]: 3600s, 3500sh, 3395, 3335, 3220s, 3140, 2925, 1660sh, 1592w, 1420sh, 1395s, 1301, 1281, 1190, 1135sh, 1100, 1084, 1060sh, 1050sh, 992s, 966s, 955sh, 887s, 858, 8
Notes:
Virtually insoluble in cold water. Partially dissolved by prolonged submersion in boiling water.
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 Hydroboracite
mindat.org URL:
https://www.mindat.org/min-1967.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Hydroboracite
Reference List:
Larsen, Esper S. (1921) The microscopic determination of the nonopaque minerals. Bulletin 679. US Geological Survey doi:10.3133/b679 p.88
Sabelli, C., Stoppioni, A. (1978) Refinement of the crystal structure of hydroboracite. The Canadian Mineralogist, 16 (1) 75-80
Localities for Hydroboracite
Showing 51 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.
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Rio Tinto Borax Mine, Kramer Borate deposit, Boron, Kern County, California, USA