Ulexite

Big Photo

California, USA
8.89 carats
© Rarestone.com

Ulexite is named after G.L. Ulex, German chemist who performed the first correct analysis of the mineral.

Ulexite is called the "TV rock" or "television stone" for its its unusual optical characteristics. Each thin fibrous crystal acts as an optical fibre, transmitting light along its length by internal reflection. A piece of writing placed underneath the stone appears on the surface.

Ulexite decomposes in hot water.

Ulexite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 

Ulexite Gemstones by Size

This table shows distribution of Ulexite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:4.71 cts
Heaviest:8.89 cts
Average:6.73 cts
Total photos:3
Do you have a larger Ulexite? Why not upload a photo?
4.71ct to 5.13ct5.13ct to 5.55ct5.55ct to 5.96ct5.96ct to 6.38ct6.38ct to 6.80ct6.80ct to 7.22ct7.22ct to 7.64ct7.64ct to 8.05ct8.05ct to 8.47ct8.47ct to 8.89ct
General Information
Chemical Formula
NaCaB
 
5
O
 
6
(OH)
 
6
· 5H
 
2
O
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Ulexite
Mohs Hardness2 to 2.5
Walter Schumann, Gemstones of the world (2001)
More from other references
Specific Gravity1.65 to 1.99
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
TenacityBrittle
Anthony et al, Handbook of mineralogy (2001)
Cleavage QualityPerfect
Walter Schumann, Gemstones of the world (2001)
More from other references
FractureUneven
Anthony et al, Handbook of mineralogy (2001) Uneven across fiber groups
Optical Properties of Ulexite
Refractive Index1.491 to 1.520
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Optical CharacterBiaxial/+
Michael O’Donoghue, Gems, Sixth Edition (2006)
Birefringence0.029
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
ChatoyancyYes
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)White
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
TransparencyTransparent,Translucent
Walter Schumann, Gemstones of the world (2001)
More from other references
LustreSilky
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Fluorescence & other light emissions
Fluorescence (General)May fluoresce yellow, greenish yellow, cream, white under SW and LW
Anthony et al, Handbook of mineralogy (2001)
Fluorescence (Short Wave UV)Blue, green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Ulexite
Crystal SystemMonoclinic
Walter Schumann, Gemstones of the world (2001)
More from other references
HabitFibrous crystals
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Geological Environment
Where found:Ulexite occurs in dry lakes and playa deposits, with other borates.
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Further Information
Mineral information:Ulexite information at mindat.org
Significant Gem Localities
USA
 
  • California
    • Kern Co.
      • Kramer District (Kramer Borate District)
Gemstones of the world, W.Schumann, 2001, p 202
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