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Ulexite
Current inventory:  0 gems
 

Chemistry:  NaCaB₅O₆(OH)₆·5(H₂O)

Discovered in 1850;   IMA status: Valid (pre-IMA; Grandfathered).
Ulexite is named in honor of George Ludwig Ulex (1811–1883), German chemist who obtained the first reliable analysis of the mineral.

Classification

Mineral Classification:

Borates

Strunz 8th Ed. ID:

5/H.14-10

Nickel-Strunz 10th Ed. ID:

6.EA.25

6 : BORATES
E : Pentaborates
A : Neso-pentaborates

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Rare as measurable crystals, which may have many forms; typically elongated to acicular, to 5 cm, then forming fibrous cottonball-like masses; in compact parallel fibrous veins, and radiating and compact nodular groups.

Twinning:

Polysynthetic

Physical Properties

Cleavage:

[010] Perfect, [110] Perfect

Fracture:

Irregular, Uneven across fiber groups

Tenacity:

Brittle

Moh's Hardness:

2.5

Density:

1.95 - 1.96 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White

Transparency:

Transparent, Translucent, Opaque

Luster:

Vitreous, Silky, or Satiny in fibrous aggregates

Refractive Index:

1.491 - 1.520  Biaxial ( + )

Birefringence:

0.028

Dispersion:

None

Pleochroism:

None

Occurances

Geological Setting:

Typically in playa and salt-marsh deposits in arid regions and bedded sedimentary deposits formed from these, the boron supplied from surrounding hot springs. Some occurrences contain upwards of one billion tons of Ulexite.

Common Associations:

Borax, Calcite, Colemanite, Glauberite, Gypsum, Halite, Hydroboracite, Meyerhofferite, Mirabilite, Probertite, Trona

Type Locality:

Iquique Province, Tarapacá Region, Chile

Year Discovered:

1850

View mineral photos:

Ulexite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Ulexite is a rare borate mineral very similar to Hydroboracite. They both commonly form as silky, fibrous crystal clusters and are not easy to distinguish. Ulexite is an interesting mineral in that is very fibrous and the fibers are transparent along their length and packed tightly together so that they act like an array of parallel glass fibers. If the material is polished perpendicular to the fiber direction, a piece of Ulexite will transmit an image from the bottom of the piece to the top. This optiacal phenomenon is the reason Ulexite has been nicknamed TV stone. Ulexite pieces are typically cut and polished only on the ends as a novelty item. Cats Eye cabochons are also available. Faceted gems are extremely rare because the material is usually too fibrous to facet.

The most notable occurances of Ulexite are Bigadiç Mine, Bigadiç, Balikesir Province, Marmara Region, Turkey; Boron Pit, U.S. Borax Mine, Boron, Kramer District, Kern County, California, USA; Anniversary Mine (Callville Wash), White Basin, Muddy Mountains District, Clark County, Nevada, USA.
 

  
Ulexite gems for sale:

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