Boron

In nature, boron is found in the Earth's crust, ~10 ppm [7]. Boron does not occur naturally in its elemental form but occurs boric acid B(OH)₃ or H₃BO₃. In volcanic regions boron also occurs as the minerals borax, Na₂B₄O₇ · 10 H₂O, kernite, Na₂B₄O₇ · 4 H₂O, and colemanite Ca₂B₆O₁₁ · 5 H₂O [6]. The isotopes found in nature are ¹⁰B (19.9 %, stable) and ¹¹B (80.1 %, stable) [7,8]

In pure solid form, boron exist in the following forms:
α-rhombohedral structure [7]
β-rhombohedral structure [7]
α-tetragonal structure [7]

Boron can be made by reduction of the oxide B₂O₃ using magnesium [6].

B₂O₃ (s) + 3 Mg (s) 2 B (s) + 3 MgO (s) The MgO is removed by dissolving it in hydrochloric acid.


Boron can also be made by passing a mixture of boron trichloride and hydrogen through and electric arc or over a hot tungsten filament (1500 °C) [6]

2 BCl₃ (g) + 3 H₂ (g) 2 B (s) + 6 HCl (g)