The Round Mountain Gold deposit is a very large, epithermal, low-sulfidation, volcanic-hosted, hot-springs type, precious metal deposit, interpreted to be located along the margin of a buried volcanic caldera. The deposit genesis is intimately associated with the Tertiary volcanism and caldera formation. Intracaldera collapse features and sympathetic faulting in the metasedimentary rocks provided the major structural conduits for gold-bearing hydrothermal fluids. In the volcanic units, these ascending fluids deposited gold along a broad westnorthwest trend.

Gold mineralization within the Round Mountain deposit occurs as electrum in association with quartz, adularia, pyrite and iron oxides. Shear zone fractures, veins and disseminations within the more permeable units (typically open pumice sites) host the mineralization. Primary sulfide mineralization consists of electrum associated with or internal to pyrite grains. In oxidized zones, gold occurs as electrum associated with iron oxides, or as disseminations along fractures.

Alteration of the volcanic units within the Round Mountain deposit can be characterized as a continuum from fresh rock progressing through chlorite, clay, sericitic+quartz, adularia+quartz+sericite, and quartz+adularia alteration assemblages. The alteration is zoned outward from potassic at the center to propylitic on the margin. There is a reasonable correlation between increasing gold grades and increasing degrees of alteration. The central ore zone is characterized by pervasive K-feldspar found replacing the rock groundmass, replacing primary sanidine, or as crystal growths in open-space.

Ore zones within the metasediments are more subtle, largely defined by secondary quartz overgrowths, pyrite and adularia associated with narrow northwest-trending structures.

Ore-grade mineralization is also present in the Stebbins Hill unit as silicified breccias with strong argillic alteration.

The Round Mountain deposit includes the Los Gazabo Vein, Keane Vein, Mariposa Vein sheeted zone, Great Western sheeted zone, Black Hawk sheeted zone, 921 Section, 471 Vein, and Fault Fissure vein. The veins were so closely spaced as to form sheeted zones; the dips of veins steepen and change with depth. Gold grade of ore has a positive correlation with the abundance of NW-striking joints. The ore-hosting tuff consists of a 400 to 500 foot thick non-welded base, a densely welded central portion about 800 feet thick, and a less densely welded vapor-phase altered top that is 75-100 feet thick. Where narrow fractures cut the lower, non-welded portion, mineralization occurs as thin quartz veinlets and as disseminations throughout the pumiceous tuff. In the welded portion, mineralization occurs wholly as veins along high angle fractures or along hydrothermally dilated low angle joints. Dip of the ain ore body is 15SW at cap, 85SW at base.

Gold is intergrown with vein quartz associated with limonite and minor manganese oxide in small fissures. Visible gold often occurs on projecting quartz crystals in drusy cavities and is distinctly crystalline, usually in fairly well defined octahedral and more complex forms. Gold on adularia was observed in specimens from the rich veinlets on the top of Round Mountain.

The Round Mountain mine currently operates a conventional open pit that is approximately 10,700 feet long in the north-west, south-east direction and 8,800 feet wide. The operation uses conventional open-pit mining methods.

Round Mountain uses conventional open-pit mining methods and recovers gold using four independent processing operations. These include crushed ore leaching (reusable pad), run-of-mine ore leaching (dedicated pad), milling and the gravity concentration circuit. Most of the ore is heap leached, with higher grade oxidized ores crushed and placed on the reusable pad. Lower grade ore, ore removed from the reusable leach pad, and stockpiled ore that was previously leached are placed on the dedicated pad.

Mill represents ~15% of production:
• Capacity: 12,000 t/d;
• Primarily used to treat sulfide ore;
• Unconventional mill - only a small portion of mill feed is treated with cyanide
* Majority of gold (~90%) recovered from carbon-in-pulp circuit
* Remainder of gold recovered with gravity separation (spirals, tables and gold wheels)
• Average grade: 1 g/t;
• Average recovery: 80 to 83%;
• Mill expected to run to 2022.

Heap leach ope ........