Although the Sierra Madre del Sur is comparatively less well-endowed in silver resources than the regions to the north, there are a few properties with significant amounts of the white metal, adding up to more than half a billion ounces. Silver is contained in different deposit types, like skarns, VMS, porphyry coppers, and epithermal veins of intermediate and low sulfidation affinities. Silver is mined as a primary ore in epithermal deposits, both intermediate and low sulfidation, and in VMS deposits. Average grade varies from 45 to 230 g/t Ag for intermediate sulfidation epithermal deposits, whereas for low sulfidation deposits the spread is form 119 to 235 g/t Ag, and from 100 to 217 g/t in VMS deposits. The skarns in and out of the Guerrero Gold Belt carry some silver as by-product, in the 5 to 25 g/t range, whereas porphyry coppers have lower grades, in the range of 1 to 2 g/t.
No silver resource towers over the others in the Sierra Madre del Sur, as is the case for gold. The largest two deposits are Goldcorp’s Los Filos in Guerrero, which carries 110.7 M Oz Ag, and Fortuna Silver’s San Jose in Oaxaca, with 102.8 M Oz Ag. The first a skarn with silver as by-product and the second a primary silver producer from a low sulfidation epithermal vein system. The next three in size are the VMS of Rey de Plata, Tizapa and Campo Morado, at 73.5, 71.3 and 56.2 M Oz Ag respectively, where silver provides a good share of the value of the polymetallic mineralization. The porphyry copper of La Verde carries just over 2 g/t silver, that add up to 52 M Oz Ag, while the skarns of Media Luna and Cobre Grande carry grades of 26.6 and 12.9 g/t for a silver resource of 44 .0 and 21.0 M Oz respectively. There are nine more deposits with published silver resources in the Sierra Madre del Sur, each with between 3.3 and 16.8 M Oz silver, as can be seen on the table below.