Elemental Boron and Refractory Boron Compounds

Elemental boron is a refractory material that is usually isolated either as a shiny black crystalline solid or a softer, browner, more impure amorphous solid. Reduction of readily available boron compounds containing boron–oxygen bonds to elemental boron is energy intensive and costly - http://www.science-chemistry.com/elemental-boron-and-refractory-boron-compounds