Borax
A valid IMA mineral species - grandfathered
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About Borax
Formula:
Na2(B4O5)(OH)4 · 8H2O
Colour:
Colourless, grey, white, yellowish, seldom bluish or greenish; colourless in transmitted light.
Lustre:
Vitreous, Resinous, Earthy
Hardness:
2 - 2½
Specific Gravity:
1.715
Crystal System:
Monoclinic
Name:
From the Arabic bauraq, meaning "white", which also included niter and natron of the time.
Type Locality:
Unique Identifiers
Mindat ID:
722
Long-form identifier:
mindat:1:1:722:1
IMA Classification of Borax
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Na2B4O5(OH)4·8H2O
Classification of Borax
6.DA.10
6 : BORATES
D : Tetraborates
A : Neso-tetraborates
6 : BORATES
D : Tetraborates
A : Neso-tetraborates
26.4.1.1
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
4 : Tetraborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
4 : Tetraborates
9.1.9
9 : Borates
1 : Borates of the alkalis and boric acid
9 : Borates
1 : Borates of the alkalis and boric acid
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 for Standard |
|---|---|---|
| Brx | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Brx | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Pronunciation of Borax
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Borax
Vitreous, Resinous, Earthy
Transparency:
Translucent, Opaque
Colour:
Colourless, grey, white, yellowish, seldom bluish or greenish; colourless in transmitted light.
Streak:
White
Hardness:
2 - 2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {100} perfect; on {110} less perfect; on {010} in traces.
On {100} perfect; on {110} less perfect; on {010} in traces.
Fracture:
Conchoidal
Density:
1.715(2) g/cm3 (Measured) 1.7 g/cm3 (Calculated)
Comment:
Measured density of the pure chemical compound
Optical Data of Borax
Type:
Biaxial (-)
RI values:
nα = 1.4466 nβ = 1.4687 nγ = 1.4717
2V:
Measured: 39° to 40°, Calculated: 32° to 40°
Max. Birefringence:
δ = 0.025
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 (negative)
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
Optical Extinction:
X = b; Z ∧ c = –55°35′.
Chemistry of Borax
Mindat Formula:
Na2(B4O5)(OH)4 · 8H2O
Element Weights:
Elements listed:
Crystallography of Borax
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Cell Parameters:
a = 12.2012(2) Å, b = 10.644 Å, c = 11.879 Å
β = 106.617(1)°
β = 106.617(1)°
Ratio:
a:b:c = 1.146 : 1 : 1.116
Unit Cell V:
1,478.29 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals commonly short-prismatic [001] and often rather tabular {100}. Prominent zones [001] and [110]. Faces "m," "o," and "z" often striated parallel to [110]. Crystals often malformed through abnormal development of part of one or more zones.
Twinning:
On {100}, rare.
Crystallographic forms of Borax
Crystal Atlas:
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Borax no.8 - {100} - Goldschmidt (1913-1926)
Borax no.11 - {100} - Goldschmidt (1913-1926)
Borax no.28 - {100} - Goldschmidt (1913-1926)
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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) |
|---|---|---|---|---|---|---|---|
| 0009647 | Borax | Levy H A, Lisensky G C (1978) Crystal structures of sodium sulfate decahydrate (Glauber's salt) and sodium tetraborate decahydrate (borax). Redetermination by neutron diffraction Acta Crystallographica B34 3502-3510 |  | 1978 | Synthetic | 0 | 293 |
| 0019358 | Borax | Morimoto N (1956) The crystal structure of borax Mineralogical Journal 2 1-18 | 1956 | synthetic | 0 | 293 | |
| 0019359 | Borax | Gainsford G J, Kemmitt T, Higham C (2008) Redetermination of the borax structure from laboratory X-ray data at 145 K Acta Crystallographica E64 i24-i25 | | 2008 | synthetic | 0 | 145 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.576 Å | (100) |
| 2.565 Å | (95) |
| 4.86 Å | (80) |
| 2.848 Å | (65) |
| 2.833 Å | (60) |
| 5.69 Å | (50) |
| 3.936 Å | (45) |
Comments:
Synthetic.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
In evaporite deposits, salt lakes, playas, and efflorescences on soils in arid regions, in solution in hot springs.
Type Occurrence of Borax
Synonyms of Borax
Other Language Names for Borax
Armenian:Buraq
Bengali:বোরাক্স
Bosnian:Boraks
Catalan:Bòrax
Czech:Tetraboritan sodný
Dutch:Borax
Esperanto:Borakso
Farsi/Persian:Būrah
French:Borax
Soude boratée
Soude boratée
Galician:Bórax
Hindi:Tinkál
Hungarian:Bórax
Indonesian:Bleng
Irish Gaelic:Bórás
Italian:Borace
Japanese:ホウ砂
Latin:Borras
Lithuanian:Boraksas
Polish:Boraks rodzimy
Portuguese:Bórax
Romanian:Borax
Russian:Бура
Serbian:Боракс
Simplified Chinese:硼砂
Spanish:Bórax
Swedish:Borax
Traditional Chinese:硼砂
Turkish:Boraks
Ukrainian:Бура
Vietnamese:Borac
Common Associates
Associations Based on Photo Data:
| 30 photos of Borax associated with Tincalconite | Na2(B4O7) · 5H2O |
| 7 photos of Borax associated with Ulexite | NaCa[B5O6(OH)6] · 5H2O |
| 6 photos of Borax associated with Sulphohalite | Na6(SO4)2FCl |
| 4 photos of Borax associated with Hanksite | Na22K(SO4)9(CO3)2Cl |
| 2 photos of Borax associated with 'Unnamed (Antimony Sulphide)' | (Sb,S) |
Related Minerals - Strunz-mindat Grouping
| 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.40 | Borcarite | Ca4Mg(B4O6(OH)6)(CO3)2 |
| 6.DA.60 | Fontarnauite | (Na,K)2(Sr,Ca)(SO4)[B5O8(OH)] · 2H2O |
Other Information
IR Spectrum:
Siberian material [cm-1]: 3510s, 3410s, 3200sh, 1660sh, 1640, 1413s, 1385sh, 1330sh, 1180sh, 1127, 1070s, 1025sh, 996, 855sh, 830sh, 807, 760sh, 687sh, 652sh, 610
Magnetism:
Diamagnetic
Thermal Behaviour:
Melting point: 878 °C. The melt dissolves numerous metal oxides.
Loses 5 mol of water when heated to 100°C, another 4 mol when heated to 150 °C, and the last mol at 400 °C.
Loses 5 mol of water when heated to 100°C, another 4 mol when heated to 150 °C, and the last mol at 400 °C.
Notes:
Rapidly dehydrates in air to tincalconite. Soluble in water - slightly in cold water readily in boiling water. Insoluble in ethanol.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Boron ore
Borax in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Borax
mindat.org URL:
https://www.mindat.org/min-722.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Borax
Reference List:
Haüy, René Just (1801) Traité de Minéralogie (1st ed.) Vol. 2. Chez Louis.p.366 - as Soude boratée
Phillips, Wm. (1818) Elementary Introduction to Mineralogy, second edition: 141 (as Borate of soda).
Mohs, Frederick; Haidinger, William (1825) Treatise on Mineralogy Vol. 2. p.52 - as Prismatic borax-salt
Levy, H. A., Lisensky, G. C. (1978) Crystal structures of sodium sulfate decahydrate (Glauber's salt) and sodium tetraborate decahydrate (borax) Redetermination by neutron diffraction. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 34 (12) 3502-3510 doi:10.1107/s0567740878011504
Jun, Li, Shuping, Xia, Shiyang, Gao (1995) FT-IR and Raman spectroscopic study of hydrated borates. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 51 (4) 519-532 doi:10.1016/0584-8539(94)00183-c
Localities for Borax
Showing 88 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