Ferroboron: Colemanite Reduced by Ferrosilicon above 2000 °C in an Arc Furnace (Hansen, GE, US 982,135, 1911)

Ferroboron should carry little carbon, so Hansen reduced the boron mineral colemanite with silicon instead of coke. The silicon takes the oxygen, joins the lime as a calcium silicate slag, and the boron goes into the iron of the ferrosilicon. Result: ferroboron, low in carbon, under a clean slag. Source: Hansen, US 982,135 (1911). Not given: weights, boron content. Picture drawn by Youblob.