The 10 square-mile Monte Cristo property is located in the historic Gilbert mining district, on the northeastern side of the Monte Cristo Range in Esmeralda County, Nevada, approximately 24 miles west-northwest of Tonopah, Nevada. The property and the surrounding area have been the focus of precious metal exploration and small-scale mining since the discovery of high-grade epithermal gold mineralization near the Gilbert town site in 1924.
The earliest record of mining in the Gilbert mining district is from the 1890’s at the Carrie mine which produced small amounts of lead and silver. There, shallow underground workings exploited galena and tetrahedrite bearing quartz veins. When gold was discovered in 1924 limited production occurred from shallow underground mining on the Last Hope, Black Mammoth and Monte Cristo vein structures. Modern exploration began in the early 1970’s focused on porphyry copper mineralization leading to the discovery of open pit minable gold in the early 1980’s. By 1988, Kincaid Exploration and Mining Co (Kemco) began a heap leach operation mining from the McLean Pit. No further production has occurred since that time. Hecla acquired the Monte Cristo property in 2012.
Monte Cristo sits within the Walker Lane structural belt and is host to epithermal gold and silver mineralization in at least four, sub-parallel, north-northeast-trending vein structures (McLean Lode, Last Hope, Black Mammoth, and Monte Cristo). These sub-parallel mineralized vein structures appear to be controlled by a district-wide strike-slip fault (Gilbert-Norman Mill fault zone) striking north-northeast to north-south that separates slightly older Tertiary rhyolitic pyroclastic units, rhyolite dikes, and rhyolite domes on the east from younger Tertiary andesitic flows and lahars on the west.
Large areas of acid sulfate alteration occur at surface along the district-wide strike-slip fault and have been the focus of historic and recent exploration activities. Gold and silver mineralization is hosted in a series of episodic quartz veins, vein breccias, fluidized breccias, and stockwork zones. Native gold associated with or without pyrite in quartz veining is the most important gold mineralizing style at Monte Cristo.
Exploration activities Since Hecla acquired the property in 2012 includes detailed geologic mapping, limited rock chip and soil sampling, re-logging of over 38,000 feet of historic drill core from the property, and limited core drilling. Through this work, priority 1 targets have been identified including the Black Mammoth target, Norman Mill target, and extensions to the McLean Lode resource target areas.
The Monte Cristo property package will continue to be systematically explored and evaluated during the next several years. This continued exploration and evaluation will include additional detailed geologic mapping, rock chip and soil sampling, continued target specific and district wide geologic cross-section generation and interpretation, drill testing of priority 1 targets, and advancing lower priority targets to the drill testing stage.