III ), ▁often ▁associated ▁with ▁other ▁elements . ▁More ▁than ▁one ▁hundred ▁bor ate ▁min er als ▁contain ▁bor on ▁in ▁ox id ation ▁state ▁+ 3 . ▁These ▁min er als ▁res emble ▁sil ic ates ▁in ▁some ▁respect , ▁although ▁bor on ▁is ▁often ▁found ▁not ▁only ▁in ▁a ▁t etra hed ral ▁coord ination ▁with ▁o xygen , ▁but ▁also ▁in ▁a ▁trig onal ▁plan ar ▁configuration . ▁Un like ▁sil ic ates , ▁the ▁bor on ▁min er als ▁never ▁contain ▁bor on ▁with ▁coord ination ▁number ▁greater ▁than ▁four . ▁A ▁typical ▁mot if ▁is ▁exempl ified ▁by ▁the ▁t etra bor ate ▁an ions ▁of ▁the ▁common ▁min eral ▁bor ax , ▁shown ▁at ▁left . ▁The ▁formal ▁negative ▁charge ▁of ▁the ▁t etra hed ral ▁bor ate ▁center ▁is ▁bal anced ▁by ▁metal ▁c ations ▁in ▁the ▁min er als , ▁such ▁as ▁the ▁sod ium ▁( Na +) ▁in ▁bor ax . ▁The ▁tour mal ine ▁group ▁of ▁bor ate - sil ic ates ▁is ▁also ▁a ▁very ▁important ▁bor on - b ear ing ▁min eral ▁group , ▁and ▁a ▁number ▁of ▁bor os il ic ates ▁are ▁also ▁known ▁to ▁exist ▁naturally . ▁ ▁Bor anes ▁are ▁chemical ▁comp ounds ▁of ▁bor on ▁and ▁hydro gen , ▁with ▁the ▁generic ▁formula ▁of ▁B x Hy . ▁These ▁comp ounds ▁do ▁not ▁occur ▁in ▁nature . ▁Many ▁of ▁the ▁bor anes ▁readily ▁ox id ise ▁on ▁contact ▁with ▁air , ▁some ▁viol ently .