Experimentally, and somewhat controversially, boron is to date the only element besides carbon than can form a material harder than diamond. Long available to industry, ordinary boron nitride is a substance whose claim to fame is being second only to diamond in hardness. A few years ago a team of scientists produced some crystals of an exotic variant named Wurtzite boron nitride which reportedly bested the champ by 18%. Those claims have yet to receive widespread confirmation from the scientific community on account of the extreme difficulty in preparing samples large enough to experiment on. As it is, growing pure crystals of the most common type of boron nitride is breath-takingly expensive - and this is evidently child’s play compared to the challenge of creating the Wurtzite type!

Elemental boron, as shown here, is itself a supremely hard material but it is quite brittle. Given the high cost of extraction and the difficulty of working with it, there’s little appetite for engineers to put it to use. On the few occasions where nothing else is adequate, this type of crushed crystalline boron makes for an excellent abrasive. It is often also the starting point from which researchers go on their quests to seek more exotic forms of this element.