Prior to exercising the option agreement in 2005, Great Panther conducted a 30-hole (7,437-metre) diamond drilling program that tested five separate areas on the property. Three of these areas, Las Trancas, Don Benito and Hormiguera represent portions of the same vein that extends for more than four kilometres across the property. The two other areas represent parallel vein systems approximately one kilometre to the northwest (Argentina) and two kilometres to the southeast (El Rosario). Several other veins are known on the property.
Since 2005, continued drilling has been conducted to extend the mining potential of known veins and explore other veins. The acquisition of the 94-hectare La Prieta concession in the Topia District in late 2009 was a strategic move that should lead to additional production once drilling has been completed and a mine plan put in place. La Prieta is within easy trucking distance of the Topia plant.
Since acquiring the Topia Mine property, sampling of the workings, and surface and underground drill programs have been ongoing. The latest mineral resource report 2012 by Roscoe Postle Associates Inc. ("RPA") is effective as of June 30, 2012.
The 2012 Measured & Indicated ("M & I") Mineral Resources total 156,000 tonnes at 806g/t silver, 1.47g/t gold, 6.48% lead and 4.29% zinc (5.60 million silver equivalent ounces). In addition, RPA estimates 273,000 tonnes of 837g/t silver, 0.8g/t gold, 5.7% lead and 3.9% zinc (9.54 million silver equivalent ounces) in the Inferred category.
The 2012 RPA mineral resource estimate provides updates for the following veins: Argentina (west, central, east, and footwall portions in the Argentina Mine), Santa Cruz, Don Benito (north, south, intermediate, and west veins in the 1522 and Crucero 9N Mines), Recompensa, Intermediate and Oliva (Recompensa and Rincon Mines), Cantarranas (Hormiguera Mine), San Jorge and San Miguel (San Miguel Mine), San Gregorio (San Gregorio, Mina 7, and Durangueno Mines), El Rosario, and La Prieta veins, plus new mineral resource estimates for the Oxidada, Oxi, Higueras, and San Pablo veins (all Durangueno Mine).
The new total contained metal for each resource category is shown in Table 1 below.
Table 1. Contained Metal (all veins):
||Ag eq oz
The Company plans to continue the systematic replacement of annual production with new resources. This "rolling resource" is typical for underground mines as it is often not cost-effective to define a large resource/reserve in advance of mining.
Mineralization within the Topia Mine is that of a typical silver-lead-zinc epithermal vein system, formed along a series of northeast trending faults within the Tertiary-aged Lower Series Volcanics. The mined vein horizon consists of quartz, galena, sphalerite and pyrite and lesser amounts of arsenopyrite, marcasite, chalcopyrite, silver-rich sulphosalts, electrum, muscovite and carbonates.
At Topia, the historically mined ore-grade or "productive" veins are confined to a limited vertical extent of 200 to 300 metres, but can extend laterally along strike for as much as 4 kilometres. This productive vein horizon grades downward into barren coarse-grained quartz, and upwards into barren, cherty, quartz-calcite-barite. Historically, the three most prolific veins on the property were the Veta Madre, Argentina and Cantarranas. The Topia District contains multiple veins, most of which lie on the Great Panther property.
The Topia Mining District is one of the oldest in Mexico, with the discovery of silver dating back to 1538. Artisanal mining continued for centuries until the Topia Silver Mine was opened in 1952 by Peñoles (now Fresnillo), Mexico's largest silver producer. Peñoles consolidated the claim ownership, built a road into the area, and constructed a 200 tonne per day mill on site. They operated the mine continuously until 1989, when they sold it to a former mine manager, who continued production on a small scale until 1999.
Total historical production for the district has been estimated at 30 million ounces of silver. The recorded production for 1952-1999 exceeds 15 million ounces of silver, as well as 18,500 ounces of gold, 48,000 tonnes of lead and 44,500 tonnes of zinc. The on-site mill complex treated the ore and produced lead and zinc concentrates that were shipped to the Peñoles smelter in Torreon. Records for Peñoles' 38 years of production indicate average mill head grades of 437 g/t silver, 0.87 g/t gold, 3.9% lead and 4.2% zinc. Overall average metal recoveries were silver-86%, gold-55%, lead-94% and zinc-85%.