Smelter Fuel 1877—1930
In the 1870s the manufacture of coke became a thriving industry in southern Colorado, where coal suitable for making smelter fuel was mined on a large scale. Oven operations expanded in Las Animas and spread to Gunnison, Garfield, La Plata, and Pitkin Counties. In 1918, coke-making shifted largely from coal fields to the principal industrial site where the fuel was consumed, but the sources of metallurgical coal remained unchanged.
The first reduction furnaces to extract gold and silver from complex and compound ores utilized charcoal as fuel. At Leadville, one of Colorado's early smelting centers, furnaces used large quantities of the fuel made by carbonizing wood. The Grant smelter consumed 125,000 bushels monthly in 1881. Three plants used an average of about 100,000 bushels each month, and others burned smaller amounts. At that time, the price of charcoal varied from 12 to 14 cents a bushel.
Charcoal was readily available and relatively inexpensive. In the mountain district, at least for a time, abundant timber could be carbonized economically by burning it with limited access to oxygen in conical or domed kilns. However, during the ore reduction process, charcoal often produced uneven heat, creating what were called “hot tops.” When that occurred, there was a large loss of molten metal. In addition, furnace charges