This is to prevent cave-ins. The miners carry whelk-shell lamps and wield chisels in search of the lode. They may penetrate one or two hundred feet. One cannot predict how many days or months the operation will take. They may strike ore, or they may not.
Some lodes continue in an uninterrupted vein.
The ore comes in distinct types-yellow, black, purple, red, shiny, and dull. The amount of copper to be obtained from each type also varies. However, ore that is earthen is not uniform and its over-all quality cannot be determined on the basis of a single sample. To roast ore, one builds a kiln under a roof. More layers of firewood and ore are put in alternately until they reach the top of the kiln.