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Also called the "TV rock" or "television stone," ulexite is known for its unusual optical characteristics, notably its ability to transmit images through its natural fibers. A piece of writing placed underneath the stone appears on the surface of the stone! Ulexite was named for German chemist G. L. Ulex, who first correctly analyzed the species in 1850. Most specimens are milky and very poor quality, but those stones that are cut as cabochons often display a strong cat's eye effect.

Ulexite Polished
Ulexite Classification
Common Name Ulexite
Species Ulexite
Ulexite Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: None
Refractive Index 1.491-1.520
Birefringence 0.029- 0.028
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Aggregate (AGG), Doubly Refractive (DR)
Fluorescence SWUV: Inert to yellow, greenish yellow, white
LWUV: Inert to yellow, greenish yellow, white
Pleochroism None
Ulexite Characteristic Physical Properties
Hardness 2-2.5
Streak White
Specific Gravity 1.650-1.950
Toughness Poor
Inclusions Ulexite has a silky luster and tightly packed parallel fibers.
Luster Silky, Vitreous
Stability Poor
Fracture Uneven
Cleavage Perfect, in one direction, Good, in one direction, Poor, in one direction
Ulexite Chemistry & Crystallography
Chemical Name hydrous sodium calcium borate
Chemical Formula NaCaB5O6(OH)6.5H2O
Crystal System Triclinic
Chemistry Classification Borate

Ulexite Colors

  • Colorless Ulexite Colorless
  • White Ulexite White
  • Gray Ulexite Gray

Alternate Names

TV Rock, Television Stone

Countries of Origin

United States of America (the)


Avoid hot water, household chemicals, and ultrasonic cleaners

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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.