The East Durango project is located in the center of the Mexican Silver Belt, one of the most active exploration areas in Mexico due to major discoveries such as Penasquito and the nearby ECU property. The property was explored in the 1990s by Laminco and its joint venture partner, Carlin Gold. These companies identified large geochemical soil anomalies for gold, as well as the indicator elements arsenic, antimony and mercury, in an area with geologic characteristics similar to the sedimentary rock hosted gold deposits of Nevada. EXMIN performed reconnaissance mapping and sampling of the property in late 2006, which was subsequently acquired by Sierra in 2009 as part of the EXMIN acquisition.

There are many old prospect pits throughout the property, which apparently were focused on antimony exploration.

In 2008, EXMIN optioned the property to Quaterra Resources who conducted basic exploration work and drilled three diamond core holes that encountered anomalous levels of gold, silver, copper, lead and zinc. Quaterrra dropped the option in early 2015.

Subsequently, Sierra geologists have done brief reconnaissance visits to the property in order to plan the next phase of exploration work.