The Midas Property, which Hecla acquired in July 2018, is located approximately 58 miles northeast of Winnemucca, Nevada, in Elko County and covers approximately 30,000 acres and includes owned fee lands and unpatented mining claims in addition to seven lease agreements. 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. Hecla has an approved plan of operations with the BLM for exploration activities on the property and 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.
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. 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.
Modern exploration methods were employed in the district in the 1970s and 1980s by various companies, and exploration began in earnest in the early 1990s when Franco-Nevada Mining assembled a land package. Historic exploration activities include soil and rock chip sampling, surface mapping, geophysical surveying, and drilling. The official discovery of high-grade veins at Midas occurred in 1994 at the Rex Grande prospect, which grew into the Colorado Grande vein. Mine development commenced in 1997, and Franco-Nevada Mining operated the mine on behalf of the Midas Joint Venture (Franco-Nevada/Euro-Nevada) until the mine was acquired by Normandy in 2001 and then by the Newmont in 2002 in their acquisition of Normandy. Newmont operated Midas from 2002 through 2014 and the mine was acquired by Klondex in February 2014.
The existing Midas Mill uses Counter-Current-Decantation leaching method 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). 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, Newmont, Klondex, and Hecla. Production rates peaked in 2011 and declined in succeeding years along with gold grades. 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. Mine production was halted in 2019 with some remnant mining during that year.
The Midas Mine is the largest known Au-Ag epithermal deposit along the Northern Nevada Rift (“NNR”), and is located in the Midas mining district, 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 (oz/ton) 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. 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 northwest-striking veins. The veins are divided into four principal groups based on their location and orientation. The two principal groups that host the majority of the Mineral Resources are the Main Veins and East Veins. The Main Veins dip easterly and are gold dominant, while the East Veins dip to the west and contain higher silver grades than the Main Veins. The Main Veins produced more than 2.2 million ounces of gold and 26.9 million ounces of silver between 1998 and 2013, principally from the Colorado Grande and Gold Crown Veins. Initial development and production from the East Veins began in 2012. The third group of veins is comprised of the Queen and Trinity Veins located to the south of the existing workings and south of the regional South Owyhee (SOW) Fault. They are defined by limited underground and surface drill holes and there has been no mine production from them to date. The fourth group of veins is west of the Main Vein system and includes the Link and Midas Trend Veins. Like the southern vein group, these veins have yet to be mined from underground.
The Midas Mine is located on the southeast flank of the Snowstorm Mountain range near the eastern margin of the NNR structural domain, hosted in a bimodal suite of volcanic rocks. Several other structurally controlled, epithermal precious-metal vein deposits are hosted in similar Miocene-age volcanic rocks along the NNR, including Hecla’s Fire Creek Project, and Newmont’s Mule Canyon Mine (“Mule Canyon”). These mineral deposits occur along the NNR and share similar mineralization characteristics, including epithermal textures and trace-elements, locally high-grade Au and Ag, mid-Miocene ages of mineralization (15.1-15.6 Ma) and close temporal association with the Miocene host rocks.
The NNR originated at the McDermitt caldera in northwest Nevada, site of the initial eruption of the Yellowstone hot spot and propagated 500 km into southeast Nevada. The rift is readily visible on regional aeromagnetic maps as a narrow positive anomaly for approximately 250 km and is defined by an accumulation of basaltic to dacitic lava flows and dikes of mid-Miocene age. In the central portion of the rift between the Malpais Rim and Midas, John et al. (2000) defined it as a 5- to 30-km wide north-northwest-trending zone that corresponds to a magnetic high, to mafic dikes and high-angle normal faults that parallel the anomaly, and to middle Miocene volcanic flows that overlie the anomaly. The primary extension direction during rift development and magmatism at 16.5 – 15 Ma was ENE to WSW, perpendicular to the N22°W axis of the rift. These syn-rift faults sharply bound the present-day NNR on the west and decrease towards the east. From 10 Ma to about 6 Ma, the regional stress field rotated clockwise, resulting in an extension direction that was NNW-SSE. This resulted in the formation of horst and graben faults that cut the NNR to form ENE-trending grabens such as the Midas Trough, the Argenta Rim, and the Malpais Rim.
The chemical composition of the volcanic and intrusive rocks varies greatly within the rift, ranging from mafic to intermediate volcanic flows at the Malpais and Argenta Rims, mafic flows at Fire Creek, felsic tuff and andesite at Ivanhoe, and a bimodal sequence at Midas of felsic flows, tuffs and domes, and basaltic sills and dikes. Consequently, rocks from one mining district generally cannot be correlated directly with those from another, except in a time sense where high-resolution radiometric dates are available. Gold mineralization at Midas is structurally controlled by normal faults within the NNR. The style of structurally controlled mineralization observed at the Midas Mine is typical of rift-hosted epithermal style mineralization associated with an intrusive center.
|(years ended December 31)|
Information with respect to measured, indicated and inferred resources is set forth below.
|(As of December 31, 2021 unless otherwise noted)|
|(000)||(oz/ton)||(oz/ton)||(000 oz)||(000 oz)|
|Total M&I Resources (1,2)||78||5.7||0.43||444||33|
|Inferred Resources (1,2)||1,232||6.3||0.50||7,723||615|
- (footnotes)Note: All estimates are in-situ. Resources are exclusive of reserves. Totals may not represent the sum of parts due to rounding.
(1) Mineral resources for Fire Creek, Hollister and Midas are reported using $1500/oz gold and $21/oz silver prices, unless otherwise noted. A minimum mining width is defined as four feet or the vein true thickness plus two feet, whichever is greater.
(2) Midas mineral resources are reported at a gold equivalent cut-off grade of 0.237 oz/ton. Metallurgical recoveries: 90% gold, 70% silver. A gold-equivalent cut-off grade of 0.1 oz/ton and a gold price of $1700/oz used for Sinter Zone with resources undiluted.
Reporting requirements in the United States for disclosure of mineral properties as of December 31, 2020 and earlier are governed by the SEC’s Securities Act Industry Guide 7, entitled “Description of Property by Issuers Engaged or to be Engaged in Significant Mining Operations” (Guide 7). Effective January 1, 2021, the SEC has issued new rules rescinding Guide 7. Mining companies are not required to comply with the new rules until the first fiscal year beginning on or after January 1, 2021. Thus, the Company will be required to comply with the new rules when filing its Form 10-K for the fiscal year ended December 31, 2021. The Company is also a “reporting issuer” under Canadian securities laws, which require estimates of mineral resources and reserves to be prepared in accordance with Canadian National Instrument 43-101 (NI 43-101). NI 43-101 requires all disclosure of estimates of potential mineral resources and reserves to be disclosed in accordance with its requirements. Such Canadian information is included herein to satisfy the Company’s “public disclosure” obligations under Regulation FD of the SEC and to provide U.S. holders with ready access to information publicly available in Canada.
Reporting requirements in the United States for disclosure of mineral properties under Guide 7 compared to the new SEC rules (Item 1300 of Regulation S-K under the Securities and Exchange Act of 1934) and the requirements in Canada under NI 43-101 standards are substantially different. This document contains a summary of certain estimates of the Company, not only of Proven and Probable reserves within the meaning of Guide 7, but also of mineral resource and mineral reserve estimates estimated in accordance with the new SEC rules and definitional standards of the Canadian Institute of Mining, Metallurgy and Petroleum referred to in NI 43-101. Under Guide 7, the term “reserve” means that part of a mineral deposit that can be economically and legally extracted or produced at the time of the reserve determination. The term “economically”, as used in the definition of reserve, means that profitable extraction or production has been established or analytically demonstrated to be viable and justifiable under reasonable investment and market assumptions. The term “legally”, as used in the definition of reserve, does not imply that all permits needed for mining and processing have been obtained or that other legal issues have been completely resolved. However, for a reserve to exist, Hecla must have a justifiable expectation, based on applicable laws and regulations, that issuance of permits or resolution of legal issues necessary for mining and processing at a particular deposit will be accomplished in the ordinary course and in a timeframe consistent with Hecla’s current mine plans. The terms “Measured resources”, “Indicated resources,” and “Inferred resources” are mining terms as defined in accordance with the new SEC rules and NI 43-101. These terms are not defined under Guide 7 and prior to January 1, 2021, were not normally permitted to be used in reports and registration statements filed with the SEC in the United States, except where required to be disclosed by foreign law. The term “resource” does not equate to the term “reserve”. Under Guide 7, the material described herein as “Indicated resources” and “Measured resources” would be characterized as “mineralized material” and is permitted to be disclosed in tonnage and grade only, not ounces. The category of “inferred resources” is not recognized by Guide 7. Investors are cautioned not to assume that any part or all of the mineral deposits in such categories will ever be converted into Proven or Probable reserves. “Resources” have a great amount of uncertainty as to their existence, and great uncertainty as to their economic and legal feasibility. It cannot be assumed that all or any part of such a “resource” will ever be upgraded to a higher category or will ever be economically extracted. Investors are cautioned not to assume that all or any part of a “resource” exists or is economically or legally mineable. Investors are also especially cautioned that the mere fact that such resources may be referred to in ounces of silver and/or gold, rather than in tons of mineralization and grades of silver and/or gold estimated per ton, is not an indication that such material will ever result in mined ore which is processed into commercial silver or gold.
In 2022, exploration at Midas will focus on the two miles of strike length along the East Graben Corridor. Drilling will focus on wide-spaced offsets along the Racer structural corridor near intersections with the northeast oriented Owhyee structures, structural splays off the Racer structure (Vapor Trail), and the northern extension of Little Opal.