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Unpolished Vein of Ulexite

The Mineral ulexite

Gigantic crystal formations of Ulexite occur in the form of fibrous, compact veins. When polished, these specimens become the well-known "Television Stone" or "TV Stone" sold to amateur collectors. The optical effect exhibited by Television Stone is caused by each of its individual crystal fibers acting as fiber-optic cables, transmitting light from one surface to the other. Since all the fibers are parallel and compacted together, any image at below is transmitted through each crystal fiber to the top surface. For this effect to be seen, specimens are polished with smooth surfaces. Fibrous Ulexite bundles can also be carved into cabochons that display strong chatoyancy. However, due to its low hardness, it is unsuitable for gem use.
Chemical Formula NaCaB5O9 · 8H2O
Composition Hydrous sodium calcium borate
Color White to light gray
Streak White
Hardness 2.5
Crystal System Triclinic
Crystal Forms
and Aggregates
Rarely in noticeable crystals; occurs in groups of tiny crystals in rounded or lenticular aggregates. It is most commonly seen as compact, parallel, fibrous veins. Occasionally encrusting and as radial compactions of thin crystals.
Transparency Transparent to translucent
Specific Gravity 1.6 - 1.9
Luster Silky
Cleavage 1,1 - prismatic ; 2,1 - basal
Fracture Uneven to splintery
Tenacity Brittle
Complex Tests Slightly soluble in hot water. (This effect is very weak and is almost unnoticeable.)
In Group Borates; Hydrous Borates
Striking Features Silky luster, low weight and hardness.
Environment Borax evaporite deposits in dry lakes of arid regions.
Rock Type Sedimentary
Popularity (1-4) 2
Prevalence (1-3) 1
Demand (1-3) 1


 -  Variety of Ulexite from Boron, California occurring in thin, parallel, sheetlike fibers. When polished at the top and bottom, each tiny fiber transmits light through the specimen, causing anything under the specimen to appear as if it is at the top.

Ulexite is an ore of boron, and is studied in regard to its unique optical properties. "Television Stone" is highly popular as a specimen among amateur mineral collectors.

The most outstanding deposit of this mineral is Boron in the Kramer District, Kern Co., California. Enormous veins of compact fibers are found in huge quantities at this location. Rounded, cotton-like masses occur in Death Valley, Inyo Co.; and in Dagget, San Bernardino Co., California. Other Ulexite deposits exist throughout the Mojave Desert in California and parts of Nevada. Ulexite also comes from Bigadic, Turkey and the Atacama Desert in Chile.

Colemanite, Borax, Halite, Calcite, Gypsum, Glauberite

The crystal habits and mode of occurrence distinguish Ulexite from practically all other minerals. Fibrous Ulexite may resemble asbestos minerals, but it only occurs in specific localities where asbestos minerals don't exist. Ulexite may also resemble Kernite, but Kernite's unique taste can immediately differentiate between the two.

ulexite PHOTOS
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