Environmental Engineering Reference
In-Depth Information
outcrops which then dripped copper and iron, but most readers parse those
passages as poetic license.) The more likely inspiration was cooking. Min-
ers roasted ore as they might pork, boiled down liquids as they did syr-
ups, poured molten glass and iron as they might jelly. A mining complex
resembled nothing so much as a vast industrial kitchen.
Pre-industrial mining exploited fire at every turn. Prospectors burned
over hillsides to expose rock. Miners relied on fire to tunnel, to smelt, to
forge. Only the very richest and nearest mines could afford to haul raw ore
very far. Rather, they had to crush and process as much as possible on site,
and nearly every stage demanded fire.Accordingly, mines were only as good
as their fuel supply, which until recently meant wood or charcoal.The great
copper mines of Cyprus, for example, grew, cut, and regrew the surround-
ing pine forests a score of times over the centuries; the Rio Tinto mines in
Spain engorged 42 tons of wood a day, amounting to 3.2 million hectares
of woodlands over its lifetime. The origins of forestry in Sweden and
Russia lay in the state's desire to promote the growth of fuel-laden woods
around great iron mines.
Within the mining cycle, fire figures repeatedly. Georgius Agricola's great
treatise
De Re Metallica
(1556) is a grand introduction, cataloguing practices
that date from ancient times to the onset of the industrial era. Where the
veins resisted their iron picks, hardrock miners lit fires to shatter the stone
sufficiently to pry one out.This was dangerous work, requiring that mines
consider ventilation, but miners already relied on fire to illuminate the
shafts, and it was only a matter of degree to put their torches to the stone
directly. Eventually gunpowder replaced wood and steam. Yet “fire in the
hole” endured.
With fire, assayers tested the ore to determine its character and value.
With larger furnaces or pyres, some open, some enclosed, they roasted and
cooked crushed ore. The actual process varied with the properties of the
metals involved, the abundance of fuels, and local traditions. But at some
point all metallic ores would be heated either to separate them from the
country rock or to liquefy them so they could be poured and shaped; most
often both. Hotter fires required a special chamber, proper fuels (at a min-
imum, charcoal), and control over air, preferably by means of a bellows.
Eventually the furnace becomes a forge to further refine and mold.
But non-metallic stones often demanded firing as well.Turn to Vannoc-
cio Biringuccio's
Pirotechnia,
published in 1540, for a splendid survey of
fire's pervasive presence in every metallic (and any other) mining that
