For some 350 years neither technology, the newcomer patio process and the traditional smelting, managed to displace the other. The former because it could not refine argentiferous lead ores, the latter because production costs in New Spain favoured the refining of ores with a silver content around 0.2 % by way of the patio process. Ore extraction cost, and not the price of mercury but its availability, was the critical economic parameter to the patio process. Reducing the price of mercury increased the impact of salt prices on the total cost structure until they became equal in importance, around 10 % of total cost each at Regla. Fuel was a very minor contributor to the cost of the patio process. Smelting remained throughout the only viable option for ores rich in lead, with a minimum silver content of 0.3 to 0.5 %. In New Spain / Mexico the whole weight of meeting the costs of smelting fell only on silver and whatever gold was present in the ore.
The economics of refining silver did not follow the traditional lines that apply to the other commodity icons of the Early Modern period, such as cotton or sugar. The source of profit lay in factors common to modern industry: controlling operational costs and increasing the volume of production. Its producers had the guarantee that they could convert to the world’s foremost specie every single unit of silver produced. There was no further scope for technology applied in Europe to further enhance the value of this commodity. The efficiency of the mining workforce in the New World, the cost of labour, and the attrition, and those of their communities, in human lives, occupational diseases and environmental damage from mining and refining, are a hidden but very real contribution to maintaining a competitive refining cost of silver in the New World.