Ulexite (NaCa[B₅O₆(OH)₆]·5H₂O) is a hydrated sodium-calcium borate famous for its diagnostic fiber-optic property — slabs cut perpendicular to the c-axis transmit images from one face to the other, earning it the nickname “TV rock.” Forms in arid evaporite playas of California and Chile alongside borax and colemanite.
Key Facts
- Mohs hardness 2.5.
- Triclinic; fibrous and acicular crystal habit.
- Diagnostic fiber-optic property — cut slabs transmit images.
- Forms in arid playa evaporite environments.
- Companion to borax, kernite, colemanite in California-Nevada borate fields.
Notable Localities
Boron (California, USA) and the Atacama playas (Chile) are major sources. Death Valley (California) and Tincalayu (Argentina) yield collector specimens.
Found at these Localities
- Boron / Death Valley Borate District (波伦/死亡谷硼酸盐矿)
