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Springer Mine & Mill, Nevada
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LOCATION |
Imlay, Nevada USA |
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TARGET: |
Tungsten rich skarn horizons |
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COMMODITY: |
Tungsten |
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LAST UPDATED: |
June 30, 2016 |
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Project Highlights
- Underground mine and surface mill facility, 100% owned
- Current resource of 246,117 indicated tons at an average grade of 0.43% containing 106,113 STU's of
WO3 and 1,768,968 inferred tons at an average grade of 0.48% containing 852,884 STU's of
WO3, prepared in accordance with National Instrument 43-01.
- Mine/mill sized for 1,200 tpd - production capacity of 146,000 MTU
WO3 p.a.
- Located in a historic tungsten-producing district, with excellent infrastructure in place
- Environmental and operating permits largely in place to re-start facility
- Strong tungsten price, permitting status, and refurbished mill
- Available for lease or option to purchase
Overview
The Springer property is located on the east flank of the Eugene Mountains, approximately 25 miles southwest of the city of Winnemucca, and 125 miles northeast of the city of Reno, in Pershing County, Nevada. The mine site is approximately 8 miles from Interstate 80, serviced by paved/gravel road, over owned land.
The project consists of 174 lode mineral claims, 25 placer claims and fee lands for a total area of approximately 3,446 acres of fee lands. The Springer tungsten milling facility is located entirley on private fee lands.
Springer is a former tungsten production facility consisting of a 1,360-ft vertical shaft and underground workings, a 1,200 ton per day mill with automated rod/ball mill grinding and flotation circuits, plus all water rights, and most permits necessary for operation of the facility. The original construction cost on the asset in 1981 was $71 million, and EMC has invested approximately $20 million in mill and site refurbishment and upgrading/automation since 2007. A PEA completed in 2012 represents start-up production volumes with potential for future expansion. A considerably larger historic resource estimate was in place at the time of construction and ownership by GE/Utah International Inc.*
The Springer tungsten property was the site of continuous underground tungsten mining between 1918 and 1958, much of that time controlled first by the Segerstrom family, and later by the Nevada-Massachusetts Mining Company ("NMC"). Mined ore was processed on site at various mills, of which only foundations and ruins remain today. The General Electric Company ("GE") acquired the property in the 1970's, interested in securing long term tungsten supply assets to support it's lighting and industrial tools businesses. The current mine and mill were constructed by Utah International Inc. ("UII", later became BHP Minerals Group) for GE in the mid 1970's, subsequently commissioned and operated by GE for 8 months in 1982. The property has not been actively mined since October 1982, and the underground workings are currently flooded to a depth of approximately 375 feet. EMC Metals Corp. acquired the Springer mine and associated properties from GE in 2006. Between that purchase date and today, considerable refurbishment and renewal has been undertaken to the mill, control systems, hoist house, and an up-rating of the mill throughput from a nominal 950 tpd to a current 1,350 tpd capacity, and an estimated 1,200 tpd throughput after availabilities (89%).
Click here to view the Springer Mine and Mill presentation
Current Work
The existing mill at Springer has benefitted from considerable investment since the purchase from GE in 2006, although there is still important change and investment left to make prior to restart. The process flowsheet calls for the production of a 65% WO3 scheelite concentrate, using modern gravity separation techniques and traditional flotation circuits. There are no plans to utilize the digester system or the APT (ammonium paratungstate) plant on site at this time.
Permitting and environmental matters are largely in place, although the Company will require a right of way from the US Bureau of Land Management for rights to re-install a tailings pipeline to an existing tailings pond, planned to be put into service to secure mill tailings not backfilled into the mine.
A 2012 PEA plan was to employ larger scale diesel-powered rubber tire equipment of substantially greater efficiency. This reduces manpower requirements, unit operating costs, and allows better resource utilization. The mine will employ longhole mining methods (technically end slicing) and existing and new drifts will be configured to 12x12 dimension to accommodate larger gear.
Ore will be hauled and dumped into ore passes, transferred into 5 ton skips, and hoisted to the surface by a 130 TPH, 7' double drum, 400hp (DC) production hoist, for mill processing. Each mining area will have access through an adit, to surface, to permit mining equipment to be driven in and out of the mine without disassembly and installation through the shaft, which will be reserved for miner and supply access, and ore production.
The mine was allowed to flood and will require pumping out to rehab the underground areas. The total contained water has been estimated at 28,000,000 gallons, and has been tested to be mildly alkaline and containing very few minerals. Historic records indicate a low inflow of 125 gpm during operation in the early 1980's. The mine water could be utilized in the milling process, or pumped to tailings, and the necessary water rights are in place to pump out the mine.
The mine has approximately 1,084 acre-feet of water resource available from various sources. Tailings dam and structures are designed and largely constructed and in place.
Infrastructure servicing the mine is excellent. The asset is located in a mining-friendly State, 30 miles from a regional population center (Winnemucca). The proximity to Interstate Highway 80, paralleled by a main Southern Pacific railway line (siding at the ranch, 18 miles from mine gate) is a major advantage. Both Electric and natural gas connections are well established, with NV Energy (a 69kV, 3 phase, 60 Hz power line) and Southwest Gas.
Tungsten Resource
In 2016, a lease that covered a portion of the resources included in the 2012 PEA was dropped. The resources were reconciled from the 2012 PEA resource estimate and reported in a February 12, 2016 News Release. The reconciled resources showed a reduction in Indicated resources of 108,883 tons and 84,522 STU's and reduction in Inferred resources of 165,632 tons and 100,092 STUs.
| Mineral Resource Estimate |
Resource
Category |
Cut-Off Grade
WO3 |
Resource
Tons |
Grade
WO3 |
Contained Tungsten Units |
| STU's |
MTU's |
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Indicated Total
Sutton Only
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0.20% |
246,000 |
0.43% |
106,113 |
96,291 |
Inferred (All Zones)
Sutton Zone
Springer West
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0.20%
0.20% |
1,450,368
318,600 |
0.44%
0.66% |
641,652
211,232 |
583,261
191,680 |
| Total Inferred |
0.20% |
1,768,968 |
0.48% |
852,884 |
774,941 |
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On December 31, 2013 Silver Predator issued a Preliminary Economic Assessment ("PEA") with an effective date of August 20, 2012. The PEA was prepared by DMT Geosciences Ltd. of Calgary, Alberta, Canada, an indpependent mining industry consultant, and was disclosed in accordance with National Instrument 43-101(1). The Company has not completed the work necessary to update the results of the 2012 PEA with the reduced Sutton Beds tungsten resources. The company is not treating the PEA as a current measure of the potential viability of the property and the 2012 PEA estimate should not be relied upon. The PEA is referred to the reader for reference purposes only.
The mine plan in the PEA called for the conversion of the existing Sutton Mine from a cut and fill operation, as designed by the prior operator, the General Electric Company ("GE"), to a modern longhole mining operation,
more properly termed end-slicing. Sutton will be re-developed with ramps connecting drifts at various levels, modern rubber-tired equipment, and production and mine access utilizing both the existing shaft/hoist house and a new mine adit entry approaching mineralized beds from lower elevation ground to the south
The mine plan also called for a second independent mining operation at O'Byrne, on the western side of the granite intrusion, utilizing the same mining techniques and equipment, with twin adit access. The hilly topography in the western beds lends itself to declined adit entry techniques that achieve sufficient depth to make for economic development.
Click here to view the Springer Mine Preliminary Economic Assessment
Geology and Mineralization
The area is underlain by Mesozoic, meta-sedimentary rocks intruded by Cretaceous granitic rocks, which were later overlain by Tertiary volcanic rocks. The meta-sedimentary rocks are composed of peltic sediments with thin beds of micritic limestone. These limestone beds host scheelite-bearing, contact metasomatic skarn deposits. These are arranged in two general horizons each with several individual beds. The horizons strike north-northeast and dip steeply to the northwest and the southeast. Scheelite is the only tungsten mineral defined in the skarns. It occurs in early veins and as finely disseminated grains along localized marble fronts. It is also associated with later alteration of garnet and pyroxene, where it occurs as coarse-grained aggregates and fine to medium-grained, euhedral dipyramidal crystals.
Historical Exploration
The property has seen three phases of exploration work, conducted by three different owner/operators. These phases can be summarized as follows:
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Exploration drilling and underground sampling by Nevada-Massachusetts Corporation (NMC) between 1925 and 1958
- Surface and underground exploration drilling and channel sampling completed by GE between 1973 and 1982, and
- Surface diamond and reverse circulation (RC) drilling completed by EMC Metals in 2007 and 2008
The NMC exploration work focused mainly within the western-oriented mineralized beds located at the Stank and Springer-Humboldt Mines. No specific NMC sample or assay data of from any of the drifting, mining or drilling is available for any of these areas. Historic records do indicate resource grades on these beds to be higher than GE realized in the 1980's, on eastern oriented (Sutton) mineralized beds.
The exploration and sampling work completed by GE in 1981 focussed primarily on the eastern-oriented Sutton I and Sutton II areas. This work represents the majority of the exploration data available on the property. Additional work included compiling most of the older NMC data, rehabilitating certain historic underground workings, drilling 119 diamond core holes from surface and underground, extending the underground workings, and analyzing approximately 3,200 samples.
EMC Metals later (2006-2007) completed 7 diamond core holes, and an additional 251 RC drill holes - 79 holes in the Mill Beds, 51 holes in the Sutton I Beds, and 81 holes in the George Beds. All of this drill activity focussed on near surface mineralization in order to evaluate open pit potential. A few diamond core holes were also drilled in the Sutton II area for confirmation and expansion of historical resources.
Photos
References
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Springer Mine & Mill Presentation
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