Manila galleons exchanged silk and other goods for this commodity at Acapulco.  
In The Great Divergence, Kenneth Pomeranz argues that the production of this commodity was only profitable because the Single Whip Reform had led to a demand for this commodity to be imported to Ming China in large quantities.  That law replaced payments in rice and work obligations with payments in this quantity.  Manila galleons exchanged silk and other goods for this commodity at Acapulco.  Francisco de Toledo began the use of the (*) mita system at the Cerro Rico to produce this commodity at the city of Potosi.  Pieces of eight were made from this commodity.  For 10 points, identify this commodity, which along with gold sparked the Price Revolution when large amounts of it were imported to Europe from the New World.
In The Great Divergence, Kenneth Pomeranz argues that the production of this commodity was only profitable because the Single Whip Reform had led to a demand for this commodity to be imported to Ming China in large quantities.  
silver