My thanks to all those who responded, both on and off list, to my query
on the chemical effects of roasting iron ores, especially "limonites"
and carbonates. The answer, as is so often the case in iron technology,
is it depends. As I thought, the likely result is hematite or the gamma
form maghemite. Under more reducing conditions, magnetite.
I would suspect that hematite is the more common result, especially in
heap or stall roasting. Does anyone know of modern testing or
documented instances of magnetite resulting? Perhaps in a permanent
oven/roasting furnace?
Jamie Brothers
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