Ulexite (TV Rock)
Image: Andrew Silver (Public domain)
Mineral NameUlexite (TV Rock)
Chemical FormulaNaCa[B5O6(OH)6]·5H2O
Mohs Hardness2.5
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect on {010}, good on {110}
Fractureuneven
Specific Gravity1.95
Colorswhite, colorless, gray, yellowish
Transparencytransparent
Type LocalityBoron, California, USA; Death Valley, California, USA; Chile; Argentina
Mineral GroupBorates
Usessource of boron, collector's specimens, optical demonstrations
Associated Mineralsborax, colemanite, gypsum, halite
Rarityuncommon
Description
This specimen displays a white to off-white fibrous mass of ulexite, with some areas showing a radiating, translucent texture. A small label is visible on a grayish section of the matrix.
Geological Context
Ulexite is a secondary borate mineral that forms in arid regions as an evaporite in playa lakes and saline basins. It precipitates from boron-rich brines in a sedimentary environment.
