Boron | Properties, Uses, & Facts | Britannica
Properties, occurrence, and uses. Pure crystalline boron is a black, lustrous semiconductor; i.e., it conducts electricity like a metal at high temperatures and is almost an insulator at low temperatures. It is hard enough (9.3 on Mohs scale) to scratch some abrasives, such as carborundum, but too brittle for use in tools.It constitutes about 0.001 percent by weight …
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