Since 2004, the return on Pan American’s investment in mine-site exploration has been outstanding. Over the last 9 years we have added over 229.4 million ounces of new silver reserves, 20% more than we mined during the same period. We spent a total of $86.1 million for mine-site exploration during that time, adding new reserves at an average cost of approximately $0.38 per ounce of silver.
In 2012, Pan American invested $18.2 million and drilled almost 156,000 meters at our operating mines. In total, we discovered 31.2 million contained silver ounces in new mineral reserves, more than replacing the 26 million contained ounces we mined during the year. Once again, our largest reserve addition was at La Colorada, with 20.7 million ounces of silver added to proven and probable mineral reserves, net of 2012 production. La Colorada now has the second-largest reserve in our portfolio, after the recently acquired Dolores mine.
In 2013, we plan to invest $16.3 million to complete approximately 124,000 meters of diamond drilling at our mine sites. In addition, we plan to spend $14.7 million on greenfield exploration activities. The first document shows our mineral reserves and resources per mine at December 31, 2012.