Ulexite | Gemopedia

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.
Alternate
Names
TV Rock, Television Stone
Colors
White, Colorless, Gray

Ulexite Classification

Common Name

Ulexite

Species

Ulexite

Variety

Colors

White, Colorless, Gray

Alternate Names

TV Rock, Television Stone

Gemstone Groups

Key Separations

Appearance, RI and birefringence.

Comments

Ulexite will decompose in water and can be chatoyant. Ulexite is a natural fiber optic material and is called television stone because well polished stones appear to transmit writing below the stone to the surface of the stone.

Ulexite Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.491-1.52

Birefringence

0.029

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

None

Dispersion

Strength: none

Comments

Ulexite Chemistry & Crystallography

Chemical Name

hydrous sodium calcium borate

Chemical Formula

NaCaB5O6(OH)6.5H2O

Synthesis

Crystal System

Triclinic

Classification

Borate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Ulexite Characteristic Physical Properties

Hardness

2-2.5

Streak

White

Specific Gravity

1.65-1.95

Toughness

Poor

Inclusions

Ulexite has a silky luster and tightly packed parallel fibers.

Luster

Silky

Stability

Poor

Fracture

Uneven

Cleavage

Perfect, in one direction, Good, in one direction, Poor, in one direction

Comments

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