The Midas Property covers approximately 30,000 acres and includes owned fee lands and unpatented mining claims in addition to seven lease agreements located approximately 58 miles northeast of Winnemucca, Nevada, in Elko County. The Midas Property includes the underground mine, the 1,200 tons per day Merrill Crowe processing facility, related support infrastructure, and mining and milling equipment. Klondex has an approved plan of operations with the BLM for exploration activities on the property. Klondex has a second plan of operations associated with the construction of five vent raises which were designed for ventilation to remote areas of the proposed expanded underground. The mill and most of the Midas infrastructure are located on private lands.
The portal to the underground mine is located approximately one-half mile west of the mill and other site facilities. The portal provides entry to a system of declines and ramps that access the gold and silver-bearing veins. Mining levels are developed at vertical intervals of nominally 50 feet to access the mineralized vein. The mineralized material is excavated and loaded into underground haul trucks, which transport it to a surface transfer stockpile located outside the mine portal. The mineralized material is then trucked from the transfer stockpile to the main stockpile area adjacent to the mill. In the mill, the mineralized material is crushed, processed, and refined to extract gold and silver. Molten gold/silver is poured from the refinery furnace into molds, and the resulting doré is shipped off-site for refining.
||Gold and silver
production Location: Elko County, Nevada, in the historic Midas Mining District
||30,000 hectares: owned fee lands, unpatented mining claims and seven lease agreements
expansion permit for the tailings is
underway; expected in 2016 and constructed in
||In 2019, a 2.5% royalty on the mine paid
to Franco-Nevada begins, among other small
||Starting from, 2.2 million oz Gold, 28 million oz Silver
underground mining, using a combination of long hole, cut and fill, and
||Onsite 1200 tpd
capacity; conventional leach technology and Merrill Crowe precipitation, with
gravity concentration after crushing and grinding
||94% Gold, 95% Silver
The Midas mine is a modern, mechanized narrow vein mine. Design constraints included four feet minimum width for longhole stopes with development drifts spaced at 50-foot vertical intervals. Stope development drift dimensions maintained a constant height of 11 feet and a minimum width of seven feet. Cut and fill stopes are a minimum of six feet in width, and each cut is ten feet high. Mining and backfill tasks were created from all designed excavations. These tasks were assigned costs and productivities specific to the excavation or backfill task type. Alternative mining methods including shrinkage stoping and alimak stoping are being investigated. The veins at Midas can vary in thickness from a few inches to over ten feet. Potentially economic mineralization must meet standard cut-off grade criteria as well as a grade thickness criterion before it is included as a mineral resource. Grade thickness is calculated by multiplying the block true width by its equivalent grade.
The Midas Mill uses conventional leach technology and Merrill-Crowe precipitation, with gravity concentration after crushing and grinding. The mill facility is an efficient well maintained modern mineral processing plant capable of processing 1,200 tons per day (tpd). The plant is capable of operating with a minimum crew compliment resulting in cost reductions when operated at capacity. Excess milling capacity will allow the mill to process material from Klondex’s nearby properties and also from third party toll milling sources.
Toll milling of material from third party sources has been processed periodically at the Midas Mill since 2008. The focus of ongoing metallurgical testing has been to determine how these materials typically behave in processing as blended with Midas mineralization.
Midas is a historic mining district, with recorded production beginning in the early 1900s. Most accounts estimate approximately 300,000 ounces of gold and three million ounces of silver production between 1907 and 1942 when non-essential mining activity was suspended by the War Production Board. This production was from predominately underground mining of high grade veins that outcropped at surface, sporadically augmented by discoveries of placer deposits. The largest historic producer was the Elko-Prince mine in the northern part of the district. Since modern mining began in 1998, 2.2 million ounces of gold and 26.9 million ounces of silver were produced by Franco-Nevada Mining, Normandy, and Newmont. Production rates peaked in 2011 and declined in succeeding years. Gold grades have also declined, indicating Newmont’s planned depletion of the Main Veins. Silver grades increased in 2013 indicating the shift in production from the Main Veins to the East Veins where the silver gold ratio is substantially greater.