1986 Field Trip to the Fortitude Gold-Silver Mine, NV

In May 1986, I was working for Tenneco Minerals Company as an exploration geologist and visited the Fortitude gold skarn deposit in the Battle Mountain Range in Nevada. The deposit was owned by Battle Mountain Gold Corp. (BMG). The mine visit was part of a field trip part of GEOEXPO/86. The trips were add-ons to a symposium held in Vancouver, BC. The trip and symposium were sponsored by The Association of Exploration Geochemists and Geological Association of Canada. The field trips were lead by Harold (Hal) F. Bonham of the Nevada Bureau of Mines and Geology.

View northerly of the Fortitude open pit from August 1986 (Emmons).

One month earlier, July 1986, three Battle Mountain geologists: P.R. Wotruba, R.G. Benson, and K.W. Schmidt published a brief but informative description of the Fortitude deposit (Battle Mountain describes the geology of its Fortitude gold-silver deposit at Copper Canyon: Mining Engineering, p. 495-499). The benches are 20 feet high for scale.

This cross section of the Fortitude is from the above cited paper by Wotruba, et al. and the following description of the geology is summarized from the paper.




Fortitude gold-silver, sulfide-skarn deposit cross section looking due north by Battle Mountain Gold Corp. 1986.

The reserves reported by BMG in January 1985 were 11 million tons grading 0.154 opt gold and 0.83 opt silver containing 1.7 million ounces of gold and 9 million ounces of silver.

The gold-silver skarn deposit is located in the Copper Canyon area of the Battle Mountain Range. The center of the mineralized zone is occupied by an altered granodiorite pluton (Eocene, radiometric date of 38.5 Ma). An altered dike extends to the north from the Copper Canyon pluton and fills the Virgin fault. Hydrothermal alteration and metal zoning form concentric shells around the intrusion. The inner zone of alteration is potassic altering the granodiorite. The limit of this alteration is defined the limit of secondary biotite. Further out is phyllic and then propylitic alteration. Metal zoning outwards from the intrusion is: Cu+Au+Ag > Au+Ag > Pb+Zn+Ag. Fluid inclusion data indicate temperatures of >500 to 200 degrees centigrade.

The sulfide skarn is hosted by the Antler Peak Limestone (Pennsylvanian).  The deposit is stratabound (manto-like) and is distal to the source intrusion in Copper Canyon. The limestone occurs within other carbonate and clastic rocks of Permian and Pennsylvanian age. Thrust over these strata is the Havallah (previously called the Pumpernickel) sequence. The Golconda thrust is related to the Sonoma orogeny.

The mineralogy of the skarn consist of andraditic garnet, diopside, epidote, actinolite, tremolite, quartz and calcite. Sulfide mineral consist of pyrrhotite, chalcopyrite, pyrite, sphalerite, and galena. Sulfide content is locally of a massive nature. Owing to the pyrrhotite content the mineralization is magnetic and was reflected in a small aeromagnetic anomaly. This was part of the discovery story of the Fortitude deposit.

Gold Specimens from the Round Mountain Mine, Nevada

The Round Mountain gold deposit is located in central Nevada and is a low-grade, disseminated gold deposit. The mineralization is hosted by Tertiary rhyolite tuff and Paleozoic metasedimentary rocks. The deposit was discovered in the early 1900s by local prospectors. The discovery included a multi-pound gold "nugget" that was found at a badger hole on the flank of the hill of Round Mountain. Early production was by placer, open cut and underground mining. Modern production began in 1977 and continues today (2019) by open pit mining with the gold recovered by heap leaching and milling.

The mine is currently owned and operated by Round Mountain Mining Corp., a wholly owned subsidiary of Kinross Gold Corp. The gold production since 1977 exceeds 15 million troy ounces.

The Round Mountain deposit is unique in the quality of coarse, crystalline gold (electrum) specimens that it has yielded. These are a few examples of the gold from the author's collection.


Coarse gold veining with quartz vein cutting a hydrothermally altered rhyolite tuff. The vein with adularia is 26.0 Ma
and the rhyolite tuff is 26.5 Ma



Coarse gold associated with intense quartz-adularia (potassic) alteration in the non-welded pumice tuff of Round Mountain.



Crystalline gold in quartz +/- adularia vein hosted
by Paleozoic metasedimentary rocks.




Coarse crystalline gold "nugget" 
approximately 1.3 troy ounces (electrum.) 



For more information on the Round Mountain gold mine just Google it and for a satellite image search for "Round Mountain, Nevada" in Google Earth.