Since 2004, the return on Pan American’s investment in mine-site exploration has been outstanding. Over the last 10 years we have added close to 270 million new silver ounces to our mineral reserves, 20% more than we mined during the same period. We spent a total of $102.4 million on mine-site exploration during that time, adding new reserves at an average cost of approximately just $0.38 per ounce of silver.
In 2013, Pan American invested $16.3 million and drilled almost 150 kilometres at our operating mines. In total, we discovered 40.1 million contained silver ounces in new mineral reserves, far exceeding the 33.7 million contained ounces we mined during the year. Once again, our largest reserve addition was at La Colorada, with 21.7 million ounces of silver added to proven and probable mineral reserves, net of 2013 production. La Colorada now has the largest mineral reserve in our portfolio of properties.
In 2014, we plan to invest $14.8 million to complete approximately 108 kilometres of diamond drilling with special emphasis on La Colorada, Dolores, Huaron and San Vicente. In addition, we will also devote approximately $6.5 million to a few selected greenfield exploration activities. The first document shows our mineral reserves and resources per mine at December 31, 2013.