Extraction from minerals :

Principle `rightarrow` Boron may be obtained by treating borax with hot concentrated `HCl`, igniting the boric acid `H_3BO_3` to give the oxide `B_2O_3` and finally reduced with `Mg`

`undersettext(colemanite)[2Ca_2B_6O_(11)] + 3Na_2CO_3 + H_2O rightarrow 3Na_2B_4O_7 + 3CaCO_3downarrow + Ca(OH)_2`

`undersettext(Borax)(Na_2B_4O_7) + 2HCl rightarrow 2NaCl + H_2B_4O_7`

`H_2B_4O_7 + 5H_2O rightarrow 4H_3BO_3`

`2H_3BO_3 rightarrow B_2O_3 + 3H_2O`

`B_2O_3 + 3Mg rightarrow 2B + 3MgO`

Preparation :

By reducing the vapour of boron tribromide (`BBr_3`) with hydrogen in an electric arc

`2BBr_3 + 3H_2 rightarrow 2B + 6HBr uparrow`

By the thermal decomposition of `BI_3` on a tantalum filament

`2BI_3 rightarrow 2B + 3I_2`

Pure Boron in the thin film can also be obtained by heating diborane to `700^0C`

`B_2H_6 rightarrow 2B+3H_2 uparrow`

Physical properties :

(a) It is a non-metal. Boron occurs in two different allotropic forms AMORPHOUS and CRYSTALLINE

(b)Amorphous boron has not been obtained in the pure state.

(c) Crystalline boron is a black powder, extremely hard with a metallic appearance but with very low electrical conductivity.