The Hasbrouck deposit is a low-sulfidation, epithermal gold–silver deposit located in the western portion of the Divide Mining District. Host rocks are primarily tuffs and sediments of the Siebert Formation with limited mineralization within the underlying Fraction Tuff. Gold and silver mineralization consists principally of 0.1in to 1.0in wide, discontinuous silica-pyrite veinlets, sheeted veinlets and stockworks, all closely associated with larger, but erratic bodies of hydrothermal breccia. Sulfide minerals have been largely oxidized. Mineralization is accompanied by strong pervasive silicification, with associated adularia and pyrite, and has a known extent of 2,800ft east–west by 2,400ft north–south, with a maximum depth of 900ft. Mineralization is open at depth and to a limited extent to the northwest and east.

Gold occurs as electrum, as inclusions in pyrite and in goethite derived from the partial to complete oxidation of pyrite, and within siliceous gangue minerals (Graney, 1985; Hazen, 1989). Silver occurs in the native state and in argentite (Wittkopp, 1982). Silver is also intimately associated with iron oxides derived from the oxidation of silver-rich sulfide minerals that occurred as inclusions in pyrite (Wittkopp, 1982).

Hasbrouck mineralization is primarily characterized as structurally-controlled, with secondary lithologic control. West-northwest and northeast fault orientations localize higher-grade mineralization (+0.05 oz Au/ton) with lower grade material occurring as halos and straddling the clastic and tuffaceous package contact within the Siebert Formation. North-south faults appear to be late-stage or offset mineralization. Mineralization remains open at depth along the intersection of the cross-cutting structural fabrics. However, deeper drilling into the Fraction Tuff has yet to intersect significant mineralization.

Brecciated veins associated with northwest structures are dark gray to brick-red in color, and 0.05–20 inches in width. The breccia fragments are monolithic, and float in the silica matrix. Outcropping veins have the appearance of jasperoid, and strike parallel to the northwesterlytrending structural fabric. This vein type has been encountered in core holes. Banded quartz veins range from 0.05inches to as much as several inches in width. These veins parallel local structural trends, and consist of cream–white to tan to brown colored parallel bands from <0.05– 0.5 inches in width. Veins have been noted in outcrop to undulate, and follow the outer trace of large blocks of fractured rock. A vein swarm trending northeast was noted to dip both to the east and west, but not to offset each other. Stockwork quartz–sulfide veins are typically up to 0.5inch in width. Silica occurs as gray or clear quartz selvages, with a center line of sulfides (typically oxidized). Occasionally, oxidized sulfides form selvages about the veins. Rare euhedral pyrite has been noted in some veins. Veins cross cut each other, and form a crude orthogonal set. Native gold in the form of small grains was noted in one vein along the center oxidized sulfide line.

The Three Hills deposit, located in the Tonopah Mining District, is a low-sulfidation, epithermal gold deposit, and occurs in a zone of pervasive silicification within the outcropping Siebert Formation immediately above and along the contact with the underlying Fraction Tuff. Mineralization occurs in discontinuous, irregular 0.05in to 0.5in-wide veinlets, vein stockworks, and erratic breccia veins of chalcedony and quartz. Oxidation has destroyed sulfide minerals within the deposit. The currently drill-defined extent of mineralization is approximately 1,000ft east–west by 2,700ft north–south with a maximum depth of 500ft. Mineralization remains open at depth, down-dip to the east along the Siebert/Fraction Tuff contact.

Gold mineralization at Three Hills is commonly associated with areas of higher permeability lithologies, rock unit contacts, and structural features. Previous authors have described the mineralization as “disseminated” though examination of outcrops and drill core shows the higher gold grades associated with discontinuous, irregular 0.05- to 0.5inch-wide veinlets, vein stockworks, and erratic breccia veins of chalcedony and quartz. Lower gold grades in the top of the south hill are found in zones of grey to brown chalcedony, and hydrothermal breccia veins and pipes.

The pre-feasibility for the Hasbrouck project includes mining at both the Three Hills Mine and the Hasbrouck Mine. These are planned as open-pit, truck and loader operations. The truck and loader method provides reasonable costs and selectivity for these deposits. Only open pit mining methods are considered for mining at the Hasbrouck project.

The Hasbrouck heap-leach project includes two separate facilities to be located approximately 5 miles apart. The proposed Three Hills Mine will be a ROM heap-leach operation with a full recovery plant and associated infrastructure. The proposed Hasbrouck Mine will be a crushed material, heap-leach operation with mining, carbon-column adsorption and support infrastructure facilities; the proposed Hasbrouck Mine will utilize the recovery plant located at the proposed Three Hills Mine site. The proposed Three Hills Mine will be constructed first, followed by the Hasbrouck Mine.

The proposed Three Hills Mine will be a 15,000 ton per day ROM heap-leach operation. Processing at Three Hills will be by conventional heap-leaching of ROM material stacked on a single use pad. Gold will be leached from the mineralized material with dilute cyanide solution and recovered from the solution using a carbon adsorption-desorption-recovery (“ADR”) plant to produce doré bars.

The proposed Hasbrouck Mine will include a 17,500 ton per day heap-leach operation. Processing at Hasbrouck will be by conventional heap leaching of crushed material stacked on a single use pad. Gold and silver will be leached with a dilute cyanide solution and recovered from the solution using a carbon adsorption-desorption-recovery process to produce doré bars. The adsorption equipment will be located at Hasbrouck. Carbon loaded with gold and silver at the Hasbrouck adsorption plant will be loaded into bins and trucked at a rate of approximately 3tpd to Three Hills for desorption and precious metals recovery to produce doré bars. Carbon will be reactivated at the Three Hills Mine and backhauled to Hasbrouck for reuse.