Martha Mineralized Zones
Silver and gold mineralization at Martha is located within a series of quartz-rich, locally banded and brecciated, veins and veinlets. The style of mineralization has been interpreted to be intermediate-sulfidation in character (Paéz et al, 2015 and Sillitoe, 2005). The main trend of the mineralized systems is WNW and EW and dip steeply to moderately to the S, SW. On surface, mineralized structures can be several meters wide but often are much less than a meter in true width but may expand in width in the subsurface.

Base and precious metal-bearing minerals at Martha (Paéz et al, 2015 are galena, sphalerite, chalcopyrite, polybasite [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4], silver-bearing tetrahedrite, pyrargyrite (Ag3SbS3), freieslebenite (AgPbSbS3), acanthite and native silver. Pyrite and arsenopyrite are common. Gold-bearing minerals have not been identified.

Dating of base and precious mineralization is often performed by dating spatially-related minerals. At Martha, Sernageomin (2011), for Paéz’s thesis (Paéz, 2011), dated vein-hosted adularia (a low-temperature variety of orthoclase with the chemical formula KAlSi3O8) at 156.5 mya (million years ago). The host rock was dated at 157.6 mya. Alteration assemblages at Martha have been studied by several workers including the exploration staff at Coeur (Birak et al, 2007) and can be generally grouped into major sets: propylitic, silico-argillic, argillic and silicic. Cedillo Frey ........

Martha historically was predominantly an underground operation with focus on two mining locations, each with its own access portal; the Martha portal (elev. 302m) targets the Martha vein and the R4 portal (elev. 310m) gives access to the R4, Catalina, Francisca and Belen veins.

The Martha side was the original entry to the mine while the R4 portal was developed after continued exploration verified the extension of the vein system to the east. Both portals are open and utilized by Hunt today.

The lowest level of the Martha side is at 210 meters and the lowest elevation of the R4 is 145 meters. The two sides were later connected on the 210 meter. Underground mining methods consist of drifting and shrinkage (methods successfully employed at Martha in the past) and caving of crown pillar blocks and extraction of rib, footwall or hanging wall remnants. This work is accomplished without new development.  

Currently there are no underground haulage trucks and, after material has been mucked from the production face into the muck bay, transfers the rock to the surface using the mill loader.

Currently, a new 40 meter access drift is being developed using a portable jack-leg. It is targeting the underground portion of the Martha West occurrence that has so far been mined from the surface. This access is closer to the portal than the existing draw points in the Martha vein. As of April 2018 a raise is being developed from which horizontal dr ........

- subscription is required.