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NaCa[B5O6(OH)6] · 5H2O
Colourless, white, grey ...
Vitreous, Silky
Named after George Ludwig Ulex (1811-1883), German chemist, who first correctly analyzed the species.
Called the "TV" rock or "television stone" for its ability to transmit images through natural fibers. This habit is a natural fiber optic.

Typically occurs in arid regions.

Visit for gemological information about Ulexite.

Classification of Ulexite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

E : Pentaborates
A : Neso-pentaborates

5 : Pentaborates

9 : Borates
3 : Borates of Ca and Sr URL:
Please feel free to link to this page.

Type Occurrence of Ulexite

Year of Discovery:
Geological Setting of Type Material:
Playas in a desert region.
Associated Minerals at Type Locality:

Occurrences of Ulexite

Geological Setting:
Arid regions. In salt playas and desiccated saline lakes.

Physical Properties of Ulexite

Vitreous, Silky
Diaphaneity (Transparency):
Colourless, white, grey with included clays.
Hardness (Mohs):
Perfect on {010}; on {110} good; on {110} poor.
Fracture uneven across fibers.
1.955 g/cm3 (Measured)    1.955 g/cm3 (Calculated)

Crystallography of Ulexite

Crystal System:
Class (H-M):
1 - Pinacoidal
Space Group:
Cell Parameters:
a = 8.816(3) Å, b = 12.87Å, c = 6.678(1) Å
α = 90.25°, β = 109.12°, γ = 105.1°
a:b:c = 0.685 : 1 : 0.519
Small nodular, rounded, or lens-like masses; loose at times (termed "cotton balls"), comprised of acicular crystals. Fibers may be radially arranged or randomly oriented towards the centers of the masses and arranged in parallel position at the periphery. Botryoidal crusts or randomly oriented fibers. Compact veins with a parallel fibrous structure. Distinct crystals rare, greatly elongated [001] (Palache et al (1951) Dana's System of Min.: 345).
Polysynthetic, common in massive aggregates and crushed fragments. Several twin laws apply: 1. Polysynthetic on {010} and {100}; 2. {340} or {230} less certain, and others of a more complex nature.
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Ulexite

Biaxial (+)
RI values:
nα = 1.491 - 1.496 nβ = 1.504 - 1.506 nγ = 1.519 - 1.520
Measured: 73° to 78°, Calculated: 68°
Max Birefringence:
δ = 0.028
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:

Chemical Properties of Ulexite

NaCa[B5O6(OH)6] · 5H2O
Essential elements:
All elements listed in formula:

Relationship of Ulexite to other Species

6.EA.05SborgiteNa[B5O6(OH)4] · 3H2O
6.EA.05LeucostauritePb2[B5O9]Cl · 0.5H2O
6.EA.10SantiteK[B5O6(OH)4] · 2H2O
6.EA.10Ramanite-(Rb)Rb[B5O6(OH)4] · 2H2O
6.EA.10Ramanite-(Cs)Cs[B5O6(OH)4] · 2H2O
6.EA.15Ammonioborite(NH4)2[B5O6(OH)4]2 · H2O
9.3.4UralboriteCa2[B3O3(OH)5 · OB(OH)3]
9.3.8KorzhinskiteCa(B2O4) · H2O
9.3.9TyretskiteCa2B5O9OH · H2O
9.3.12InyoiteCa(H4B3O7)(OH) · 4H2O
9.3.13GoweriteCa[B5O8(OH)][B(OH)3] · 3H2O
9.3.14ColemaniteCa[B3O4(OH)3] · H2O
9.3.15PentahydroboriteCaB2O(OH)6 · 2H2O
9.3.16HexahydroboriteCa[B(OH)4]2 · 6H2O
9.3.17MeyerhofferiteCa2(H3B3O7)2 · 4H2O
9.3.18PriceiteCa2B5O7(OH)5 · H2O
9.3.19GinoriteCa2B14O23 · 8H2O
9.3.20ProbertiteNaCaB5O7(OH)4 · 3H2O
9.3.22HydroboraciteCaMg[B3O4(OH)3]2 · 3H2O
9.3.23InderboriteCaMg(H3B3O7)2 · 8H2O
9.3.24WardsmithiteCa5Mg[B4O7]6 · 30H2O
9.3.27VeatchiteSr2B11O16(OH)5 · H2O
9.3.28Veatchite-ASr2B11O16(OH)5 · H2O
9.3.29 P-Veatchite
9.3.30 BalavinskiteSr2B6O11 · 4H2O
9.3.31TunelliteSrB6O9(OH)2 · 3H2O
9.3.32Strontioginorite(Sr,Ca)2B14O23 · 8H2O

Other Names for Ulexite

Other Information

Yellow, greenish yellow, cream, white.
Other Information:
Slightly decomposed in cold water and more so in hot water, with the loss of Na to the solution.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Ulexite

Reference List:
Hayes (1844) American Journal of Science: 46: 377 (as Hydrous borate of lime).

Hayes (1844) American Journal of Science: 47: 215.

Hausmann, J.F.L. (1847) Handbuch der Mineralogie 3 volumes, Göttingen. Second edition, vol. 2, in two parts: 1429 (as Hydroborocalcite)

Ulex (1849) Ann. Chem. Pharm.: 70: 49 (as Boronatro-calcite).

Dana, J.D. (1850) System of Mineralogy, 3rd. Edition, New York: 217 (as Hayesine), 695.

Kletzinsky (1859) Polyt. Centr.: 1384 (as Tinkalzit).

How (1861) American Journal of Science: 32: 9 (as Cryptomorphite).

Des Cloizeaux, A. (1874) Manuel de minéralogie. 2 volumes and Atlas, Paris, volume 2, 1 Fasc., 208pp.: 10.

How (1877) Mineralogical Magazine: 1: 257.

Reynolds (1877) Philosophical Magazine and Journal of Science: 3: 284 (as Franklandite).

Buttgenbach (1900-1901) Société géologique de Belgique, Liége, Annales, 28, Mem. 99.

de Schulten (1901) Comptes rendus de l’Académie des sciences de Paris: 132: 1576.

van't Hoff (1907) Preuss. Ak. Wiss., Sitzber.: 303.

Foshag (1918) American Mineralogist: 3: 35.

Larsen, E.S. (1921) The Microscopic Determination of the Nonopaque Minerals, First edition, USGS Bulletin 679: 148.

Walker (1921) University of Toronto Stud., Geology series, no. 12: 54.

Mellor, J.W. (1924) A Comprehensive Treatise on Inorganic and Theoretical Chemistry. 16 volumes, London: 5: 94.

Hintze, Carl (1933) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1, [4A]: 156.

Boky (1937) Bulletin de l'Académie des sciences de l'Union des Républiques Soviétiques Socialistes, Cl. sc. mat. nat., Ser. chim.: 871.

Godlevsky (1937) Mineralogicheskoe Obshchestvo, Leningrad, Zapiski: 66(2): 315 (Min. Abs. (1938): 7: 122).

Murdoch, Joseph (1940), The crystallography of ulexite: Am. Min.: 25: 754-762 (abstract): American Mineralogist: 25: 210-211.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 345-348.

Clark, J.R. & C.L. Christ (1959), Studies of borate minerals, V: Reinvestigation of the X-ray crystallography of ulexite and probertite: American Mineralogist: 44: 712-719.

Weichel-Moore, E.J. and Potter, R.J. (1963) Fibre optical properties of ulexite. Nature: 200: 1163-1165.

Papezik, V.S. and Fong, C.C.K. (1975) Howlite and ulexite from the Carboniferous gypsum and anhydrite beds in western Newfoundland. Canadian Mineralogist: 13: 370-376.

Ghose, S., C. Wan & J.R. Clark (1978), Ulexite, NaCaB5O6(OH)6•5H2O: structure refinement, polyanion configuration, hydrogen bonding and fiber optics: American Mineralogist: 63: 160-171.

Canadian Mineralogist (1981): 19: 291.

Grew, E.S., and Anovitz, L.M. (1996) BORON: Mineralogy, Petrology and Geochemistry, second edition, as revised (2002).

Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2003) Handbook of Mineralogy, Volume V. Borates, Carbonates, Sulfates. Mineral Data Publishing, Tucson, AZ, 813pp.: 722.

Internet Links for Ulexite

The following Ulexite specimens are currently listed for sale on

Localities for Ulexite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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