This sample of borax is displayed in the Smithsonian Museum of Natural History. Borax is an oxide mineral containing boron and sodium with the composition Na2B4O5(OH)4.8H2O. The sample at left is about 6 cm across and is from Western borax mine, Boron, California. This is part of the legendary evaporite deposit in Death Valley, California. From 1883-89, 20-mule teams hauled 36.9 ton loads of borax out of Death Valley. The deposit began forming some 10,000 years ago from evaporation of a vast lake.