Rattlesnake Hills

The Rattlesnake Hills in central Wyoming are a partially exposed fragment of a synformal Archean greenstone belt that was intruded during the Tertiary by alkalic volcanic rocks.

In 1982, the WSGS discovered anomalous gold in the Rattlesnake Hills in pyrite-rich metachert. Hausel (1996) recognized a minimum of three episodes of gold mineralization, including syngenetic stratabound exhalative mineralization, epigenetic mineralization, and disseminated epithermal gold associated with Tertiary volcanic activity.

Exploration in the area by several companies between 1983 and 1993 suggested a large amount of disseminated low-grade gold thought to be more than one million ounces. Exploration also identified some higher-grade stratabound mineralization along with nearby unevaluated targets.

Exploration in the area accelerated after 2008, with efforts by several companies active in the area. The largest, Evolving Gold Corporation, eventually drilled and evaluated 252,000 ft (76,800 m) of core, finding significant gold mineralization.

geophysical surveying
2016 airborne geophysical surveying in the Rattlesnake Hills. [Credit: Wayne M. Sutherland]
Core drilling in the Rattlesnake Hills
Core drilling in the Rattlesnake Hills, 2009. [Credit: Wayne M. Sutherland]

Evolving Gold sold its property in summer 2015 to GFG Resources Inc., completing the sale in 2016. Exploration activity for gold in the Rattlesnake Hills by GFG Resources continued with an extensive airborne geophysical survey in 2016 and successful drill programs in 2016 and 2017. Exploration activities by GFG Resources are described on their website.


Patty Webber, patty.webber@wyo.gov