How to prepare amorphous boron from borax? Write equations?

Explanation

Borax on hydrolysis with dilute acids give boric acid.
Boric acid on strong heating gives boric anhydride. This boric anhydride on reduction with sodium or magnesium gives amorphous boron.
`Na_2B_4O_7+2HCl +5H_2O to 2NaCl +4H_3BO_3`
`2H_3BO_3 to^(Delta) B_2O_3+3H_2O,B_3O_3+3Mg to 2B+3MgO`