ot ope ▁is ▁ 7 B ▁which ▁dec ays ▁through ▁pro ton ▁emission ▁and ▁alpha ▁decay . ▁It ▁has ▁a ▁half - life ▁of ▁ 3 . 5 × 1 0 − 2 2 ▁s . ▁Is ot op ic ▁fraction ation ▁of ▁bor on ▁is ▁controlled ▁by ▁the ▁exchange ▁re actions ▁of ▁the ▁bor on ▁species ▁B ( OH ) 3 ▁and ▁[ B ( OH ) 4 ] − . ▁Bor on ▁is ot op es ▁are ▁also ▁fraction ated ▁during ▁min eral ▁cry st all ization , ▁during ▁H 2 O ▁phase ▁changes ▁in ▁hydro ther mal ▁systems , ▁and ▁during ▁hydro ther mal ▁alter ation ▁of ▁rock . ▁The ▁latter ▁effect ▁results ▁in ▁prefer ential ▁removal ▁of ▁the ▁[ 1 0 B ( OH ) 4 ] − ▁ion ▁onto ▁cl ays . ▁It ▁results ▁in ▁solutions ▁en rich ed ▁in ▁ 1 1 B ( OH ) 3 ▁and ▁therefore ▁may ▁be ▁responsible ▁for ▁the ▁large ▁ 1 1 B ▁en rich ment ▁in ▁se aw ater ▁relative ▁to ▁both ▁ocean ic ▁cr ust ▁and ▁contin ental ▁cr ust ; ▁this ▁difference ▁may ▁act ▁as ▁an ▁is ot op ic ▁signature . ▁ ▁The ▁ex otic ▁ 1 7 B ▁exhib its ▁a ▁nuclear ▁h alo , ▁i . e . ▁its ▁radius ▁is ▁appreci ably ▁larger ▁than ▁that ▁predicted ▁by ▁the ▁liquid ▁drop ▁model . ▁ ▁The ▁ 1 0 B ▁is ot ope ▁is ▁useful ▁for ▁capt uring ▁thermal ▁neut rons ▁( see ▁neut ron ▁cross