On a general scale, the hydrothermal system and subsequent mineralization developed at Midas is currently interpreted as a low sulfidation, epithermal precious-metal vein system, as part of a larger magmatic system at depth.

The Midas Mine is the largest known Au-Ag epithermal deposit along the Northern Nevada Rift (“NNR”) and is located, located in the mining district of Midas, also known as the Gold Circle district.

The Midas deposit consists of a series of complex steeply dipping, quartz-calcite-adularia precious metal veins hosted by volcanic and volcanoclastic rocks and locally contains mineral grades greater than (>) ten ounces per ton (opt) of gold. Gold mineralization occurs as electrum and is intimately associated with selenide and sulfide minerals. It belongs to a suite of middle Miocene low-sulfidation epithermal gold and silver mineralizing systems associated with magmatism and faulting along the NNR (Leavitt et al., 2004). The mineralization model at Midas is a shallow, low-sulfidation, vertically- and laterally-zoned, epithermal gold-silver system. Rocks in the Midas district are primarily ash flow, air-fall and lithic tuffs, felsic plugs, volcanoclastic sediments and gabbroic sills and dikes.

Gold and silver mineralization at Midas is hosted in several north-west striking veins. The veins are divided into four principle groups based on their location and orientation. The two groups hosting mineral resources are the Main Veins ........

Longitudinal sublevel (longhole) stoping has historically been the primary mining method for the five narrow Main Veins at Midas as well as the East Veins, including 905, 9052, and 805. From the portal, there are three major haulages that access these veins through eight different spirals. Generally, upper and lower sections of the same spiral connect only through ventilation/escape raises. All mineralized material produced is hauled out of the portal in trucks to a temporary stockpile where it is loaded onto a surface haul truck and delivered to the on-site mill.

Mine development is controlled by geological conditions in the area. For the sublevel stoping method, sill development is driven at a nominal seven feet wide by twelve feet high to accommodate the size of longhole drills and two-cubic yard (yd3) loaders. Where the vein thickness is wider than six feet, the sill width is increased to capture the entire vein. Sills are typically driven 600 feet north and south from the spiral cross cut. Once sills are developed, stoping begins. Stopes are drilled with a longhole drill from the floor of one level to the back of the one below, then remote mucked from the bottom level, and finally backfilled from the top level.

Typically, the mineralized material is divided into stope blocks of about four levels for development, or 200 feet vertically. Stoping begins by creating a cemented backfill barrier pillar at the bottom level of the mineralized material bloc ........

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