In 1750 the Spanish crown sent these laminating machines to the mint. They were made of oak. They were sent from Spain to Buenos Aires Argentina, and from Buenos Aires they were shipped via mule train to Potosi. Before this, African slaves and Indians would laminate the silver bars using hammers.

The rolling mills operated in a fashion similar to a clock. The energy generated below would turn a primary wheel that then distributed the energy to another series of wheels, ultimately translating into the movement of two iron rollers which laminated the silver bars. Each ingot was laminated approximately 12 times to achieve the desired thickness.

This operation was performed by 4 mules, or by 4 horses in the absence of mules. At 4,700 meters above sea level, these animals, subjected to the extreme work load, low levels of oxygen, and debilitating cold, had an average lifespan of 20-60 days. When horses and mules were not available, 20 African slaves were used to keep the wheel turning.

From 1771 onward, a coin press was used to press the laminated silver into coins. It required 8 men to work it; those men were also African slaves. Prior to this the coins were pressed using hand and hammer.

The end results of this entire process, naturally, were the pure silver coins that the Spanish crown relied upon as their primary currency. “Every peso coin minted in Potosi has cost the life of 10 Indians who have died in the depths of the mines,” wrote Fray Antonio de la Calancha in 1638.

Almost 2 billion ounces of silver were extracted from the Cerro Rico, much of which funded the Spanish Armada, a huge national debt, and other military and economic endeavors of the Spanish crown.