 It has been reported that many died of illness or accidents associated with the poor working conditions.As the ore was extremely rich, (apparently a complex mixture of oxides and sulfides of up to 15% Cu) it could be fed directly to the smelter without pre-processing other than crushing.There were 7 relatively small reverberatory furnaces in the smelter and, in the 1930s, a pair of were added to produce blister copper (98% copper).