Boron is sufficiently reactive to preclude its occurrence in the free state.the sources of combined boron are sassolite (H3 BO3), found in Italy; colemanite (Ca2B6O11.5H2O); ulexite (CaNaB5O9.8H2O); and kernite (rasorite, Na2B4O7.4H2O), in the United States. Ulexite is also found in Bolivia, Chile and Peru. Boracite (Mg7B10Cl2O30), is found in Germany. The world's major source of boron is kernite from the Mojave Desert in California, USA.