OLD MINE WORKINGS
The OMW is a POINT of the MINERALIZED STRUCTURE located approximately 10 km East from
Batopilas.
MINERA GEA has historical records of Gold production, with an average grade of 16.6 gr/ton. Attached map prepared by the engineer Emilio Bronimann (1947) graphically details the main works carried out in the Tres Hermanos Mine (depth 220m and a width 140m).
Bronimann, E. (1903) [Collection of maps relating to mines in the State of Chihuahua].1903-1957.
The Tres Hermanos mine contains two principal veins: the Veta Grande Vein striking at 329° dipping 73° NE and the Tres Hermanos Vein striking at 329° dipping 86° NE. Smaller veins crisscross the larger veins perpendicularly, striking east-west along the structure with one fault in particular that runs through the Old Mine Workings.
The two mineralized veins of the Tres Hermanos Mine were developed by upper and lower workings. The upper workings commenced in 1903 at the top of the mountain, accessed, developed, and produced mineralized material from the Veta Grande vein to the main level.
The lower eight levels were developed from 1916 to 1936 through the main level portal and a shaft with the first four levels on the Veta Grande vein and the lower four levels on the near vertical Tres Hermanos vein. The two veins merge approximately on the fourth level with the Veta Grande vein continuing vertically.
Laurence Sookochoff, PEng.
The Amalgamation Process as well as the Gold grade found in the Tailings 5.686 gr/ton, and its percentage of Copper 0.228%, are indicators of the mineral contents processed from the OMW.
Certification of the Mexican Geological Service.
Due to the aforementioned, the processed mineral contained:
- HIGH GOLD values.
- LOW COPPER veins were selected. Consequently, HIGH COPPER veins were not processed and are currently visible in the OMW.
Interior View of Mine Adit
The workings of the main level were covered by a coating of either brown to black iron oxide alteration or a mixture of iron oxides and carbonate on the roof of the workings. The mineralization exposed by sampling at the sample sites was of variable, irregular patches, and disseminations of chalcopyrite within the quartz veins and in the host rock.
Pantaleón Trejo de la Cruz reports that the Tres Hermanos Vein hosts sulfides consisting predominantly of pyrite (FeS2), chalcopyrite (CuFeS2), minor galena (PbS) and sphalerite (ZnS). The Tres Hermanos veins occur within a surficial formation of andesitic to dacitic rocks overlain by a sequence of shales and limestones.
The veins are composed of massive quartz with zones of silicified host rock and epithermal quartz indicators as banded discontinuous quartz stringers and crystalline quartz vugs. It is considered that the geneses of the veins at and above the main level are mesothermal-epithermal. This is reflected by the significantly high copper values observed as pockets, blebs, and disseminations of chalcopyrite in the quartz and the inclusive host rock, with associated low gold values.
