Aluminium Oxide Abrasive Grit: Alundum by Jacobs's Process (Stansfield, 1914)

Alundum, the artificial corundum made at Niagara Falls by the Norton Company: bauxite, calcined to drive off its water, is fused in an electric arc furnace with about 5 per cent carbon, which reduces its iron, silicon and titanium to metal nodules; the fused alumina cools slowly into a hard crystalline mass that is crushed and sized as abrasive grit. Bauxite melts near 2,000 °C and could not be melted commercially without the electric furnace. Source: A. Stansfield, The Electric Furnace, 2nd ed. (1914), pp. 357-358. Picture: the book's Fig. 143, the Higgins alundum furnace.