Ulexite is a compound mineral, a hydrated sodium calcium borate hydroxide that is closely akin, and often concurrent with borax. Both these minerals are deposited as evaporates in shallow coastal or interior desert lakes that intermittently run dry. This soft, silky white mineral has a fibrous/acicular crystal habit, which gives the rock fiber-optic properties. It is a major ore of boron. Provenance of this specimen is Nevada, actual length of sample is 140 mm, Most proliferous occurrences and mines are in the Atacama Desert of Chile and the Mojave Desert of California, USA