Ulexite

This form of ulexite is made up of closely packed fibrous crystals and transmits light well along these crystals. Ulexite also commonly forms cotton-ball like tufts of crystals. It is found with borax and is an ore of boron along with borax. It is formed by evaporation in desert areas from shallow lakes and pools when boron-rich runoff from mountains forms these temporary bodies of water.

Ulexite has the chemical name hydrated sodium calcium borate hydroxide. Its composition is

The origin of this sample of ulexite is Boron, California. Popularly called "TV stone" or "TV rock", it is transparent along the direction of the parallel fibers which form the mineral, but translucent in the perpendicular direction. This sample is about 3 x 2.3 x 0.8 cm.

This sample of ulexite is on display at the Smithsonian Museum of Natural History. It is about 8x9 cm and is from Boron, California.