 Boron is a metalloid chemical element with symbol B and atomic number 5 . Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis , it is a low @-@ abundance element in the Solar system and in the Earth 's crust . Boron is concentrated on Earth by the water @-@ solubility of its more common naturally occurring compounds , the borates . It occurs extensively in its oxidation states: as boric acid , B (OH) 3 , and as borates , the salts of boric acid .
Boron is not found free in nature , but has to be extracted chemically . The first step is the