History · Geology
About Boron / Death Valley Borate District
The Boron and Death Valley borate district in southeastern California is the world’s premier source of crystallized borate minerals — kernite, colemanite, ulexite, howlite, borax, and others. The deposits have been mined since the 1880s, including the historic “20 Mule Team” borax operations.
Geology
The borates formed in Pliocene-Pleistocene lacustrine basins where volcanic-derived B-rich hydrothermal fluids concentrated through evaporation. Boron, Calico, and the Death Valley basins each preserve distinct borate paragenesis at different stratigraphic levels.
Notable Minerals
Kernite (massive cleavable colorless to translucent), colemanite (gem-clear monoclinic crystals, sometimes large), ulexite (“TV rock” fibrous, transmits images along c-axis), howlite (white nodular, often dyed blue commercially), borax (water-soluble), probertite, tincalconite, calcite.
Collector Notes
Boron-area minerals are the global benchmark for borate species. Care: kernite, borax and tincalconite dehydrate in dry air — long-term display requires sealed containers or stable humidity.
