Dolores is an open-pit and underground silver-gold mine owned and operated
by Compañía Minera Dolores S.A. de C.V., a wholly-owned subsidiary of Pan
American Silver Corporation (Pan American). Dolores is located in Chihuahua
state, Mexico, approximately 240 kilometers west of the city of Chihuahua.
Silver and gold mineralization at Dolores is hosted in north-northwest
trending hydrothermal breccias and sheeted vein zones in the order of 5 to
10 meters wide. Most high-grade mineralization occurs along three major
structures that provided the conduit for metal-bearing fluids. Silver and
gold mineralization identified on the surface at Dolores lies over an area
4,000 meters long and up to 1,000 meters wide. The extent of mineralization
at depth and along strike has not yet been fully defined.
Mining at Dolores has been ongoing since 2008 using conventional open-pit
methods with excavators, shovels, loaders, and haul trucks. Underground
mining of the deposit by long-hole open-stoping methods occurs concurrently
with open-pit mining. Ore is crushed and conveyed to the heap leach pads at
a nominal rate of 16,200 tonnes per day.
Construction of the mine began at the end of 2006, the first doré was
produced in November 2008, and commercial production began in May 2009. The
processing facilities include a crushing plant, conveying and stacking
facilities, leach pads, solution ponds, and Merrill-Crowe and refining
facilities. Pan American completed an expansion of the Dolores mine in 2017
that featured a pulp agglomeration plant to process high-grade ore from a
new underground mine, together with the high-grade portion of the ore from
the open-pit mine.