The Pioche project, 100% owned by Altair consists of two past-producing mines, Pan American and Prince, and the 2000tpd Caselton mill with near-term production potential and significant exploration and production upside. Altair acquired these assets in 2017, securing control of a large portion of a regionally significant silver mining district known to host large tonnages of carbonate replacement silver/lead/zinc/gold mineralization. This large district has been largely under explored and under developed. The Altair properties located near the town of Pioche, the county seat of Lincoln County, Nevada benefit from excellent infrastructure.
The Caselton mill requires only minor refurbishments and capital investment. Altair aims to bring Caselton back into production in 2018 to initially process sulfide mineralized material already developed within the Pan American mine. The Caselton mill has adequate water supply, benefits from low cost grid power , and is located only 16 miles from rail at Caliente.
Pan American Mine records indicate that between 1.5 and 4.5 mt of zinc/lead/silver/gold mineralization may remain in the mine. The 1.5 million tons is within the developed mine area and the larger amount has been offset slightly downward by faulting. The remaining offset of the mineralized zone has been identified through drilling and drift sampling but will require step out drilling to guide additional development.
Left unmined on the flanks of the sulfide mineralized zones which were historically mined in the district, is a large zone of mineralization that is completely oxidized. This material when mined is potentially amenable to low cost sulfuric acid leaching to produce high grade zinc and manganese. Manganese, a valuable by-product in the Pioche ores ,may be recovered by chemical reduction ahead of, or during this leaching step. The opportunity for processing oxide ores will be evaluated in conjunction with Altair’s exploration activities in the district
Drilling at Prince in 2012 partially delineated an open-pit mineralized oxide zone and Altair’s exploration target at Prince is up to 18mt of mineralized material.
Pioche Project Exploration Targets
Note: The Pioche district exploration targets are based on historically reported zones of mineralization. Underground and surface sampling, and drilling are required to confirm and categorize any of these reported zones as a resource, and it is not known that if outlined that any such resource may be economic. Derived from Matson 2013, International Silver 2014, Hamm 1996.
Silver was discovered on the eastern slope of the Pioche Mountains in 1869 and exploited for high grade, bonanza silver ore until the 1930’s when the known fissures were fundamentally depleted. This ore occurred in brecciated fissure veins hosted in the Cambrian age Prospect Mountain Quartzite. The veins ranged in thickness from one to four feet, with swells up to ten feet. The three most productive veins extended for several thousand feet in strike and to a depth of 1200 feet.
Just to the west of the bonanza silver vein area and extending from it into exposures of stratigraphically higher limestones and shales, bedded non-oxidised sulfide replacement lead/zinc/silver mineralization was discovered. Oxidized replacements above the sulfide zone were only partially mined due to smelting issues.
The principal mines in the district were underground to develop the very large sulfide replacement “channels” or structural zones. They contain silver, zinc, lead, gold and manganese in sedimentary replacements with varying grade in each channel. The three principal channels are the Caselton or Combined Metals Channel, the Prince Channel, and the Pan American Channel. These tremendous zones of limestone replacement are known to extend for several miles in length and range from 100 feet to as much as 1,800 feet wide with individual bedded replacements up to 90 feet thick.
The Pan American Mine, last operated as a Joint Venture between the Anaconda Corporation and the Bunker Hill Company, mined an average of 1,500 tons per day of sulfide replacement ore grading 57g/t of silver and 0.14g/t of gold, 1.2% lead, 2.4% zinc, and 9 % manganese as carbonate. The ore was trucked in 80 ton capacity trailers 16 miles to the Caselton Concentrator for processing. The clean zinc concentrate contained an average of 54% zinc, and a lead/precious metals concentrate graded 60% lead with 58 ounces per ton silver. Both the lead/precious metals concentrates and the zinc concentrates, were shipped by rail to the Bunker Hill smelting and refining complex in Kellogg, Idaho.
The Caselton Concentrator facility, initially constructed in 1944 to process ores from the Combined Metals Reduction Company Caselton #2 Mine, was refurbished in 1966 to process ore from the Pan American Mine, and was again refurbished in 1976. It operated for only two years prior to closure in 1978, and has been held on a care and maintenance status since that time.
Prince is an underground mine last operated in 1949. The main shaft is 850 feet deep with several levels of drifts.