• Data Access
  • Your Email  
  • Your Email  
Keep me signed in.
Forgot your password?
Close
  • Forgot Your Password?
  • Enter the email you signed up with and we'll email it to you.
  • Your Email  
Close
Back
MDO
Mining Data Solutions
  • Home
  • Database
  • Subscribe
  • Sign In
  • Sign In
United States
Stibnite Gold Project

This page is not tailored to
devices with screen width under 750 px.
 Location:
61 km NE from Donnelly, Idaho, United States

  Project Contacts:
PO Box 429
13181 HWY 55
Donnelly
Idaho, United States
83615
Phone208.901.3060
Fax208.325.9273
WebsiteWeb
Additional Resources for Suppliers & Investors
Drill results over 30 g/t Au
Stay on top of recent discoveries.
Search drill results by commodity and grade.
Largest mines in the Americas
Mining and mill throughput capaciites.
Full profiles of select mines and projects.
Deepest underground mines
Shaft depth and mill throughput data.
Full profiles of select mines and projects.
Heavy mobile equipment
HME type, model, size and quantity.
Full profiles of select mines and projects.
Permitting and construction projects
Projects at the permitting or construction stage. Full profiles of select projects.
Mines with remote camps
Camp size, mine location and contacts.
Full profiles of select mines and projects.
Mines & projects in United States
A list of country's mines and projects.
Full profiles of select mines and projects.
  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

Thank you for browsing through mine profiles compiled by the Mining Data Online team.

Would you like to subcribe or schedule a Demo?
  • Name:
     
  • Company:
     
  • Position:
     
  • Phone:
  • Email:
  • Message:

Overview

StagePermitting
Mine TypeOpen Pit
Commodities
  • Gold
  • Silver
  • Antimony
Mining Method
  • Truck & Shovel / Loader
Processing
  • Flotation
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Pressure oxidation
  • Carbon in leach (CIL)
  • Carbon in pulp (CIP)
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
On-Site Camp 300 person
Mine Life12 years (as of Jan 1, 2014)
Latest NewsMidas Gold Completes Positive Feasibility Study for the Stibnite Gold Project, Idaho     December 22, 2020


Owners

Source: p. 12
CompanyInterestOwnership
Midas Gold Corp. 100 % Indirect
Midas Gold Idaho Inc. 100 % Direct
Midas Gold Idaho Inc. is a wholly-owned subsidiary of Midas Gold Corp.

Deposit Type

  • Skarn
  • Epithermal
  • Breccia pipe / Stockwork
  • Vein / narrow vein
  • Hydrothermal

Source: Source p.118, 125

Summary:

The origin of the wide variety of mineralization occurrences at Hangar Flats, West End, and Yellow Pine deposits is enigmatic and past workers have attributed the District metal endowment to deep seated intrusives and associated deep high temperature and high pressure processes as well as shallower lower temperature, lower pressure hydrothermal processes within an epithermal environment. However, there is no single deposit model applicable to the deposits within the District that have been discovered to date.

Mineralization occurs in numerous locations throughout the District in medium- to coarse grained, felsic to intermediate intrusive host rocks and typically occurs as disseminated replacement mineralization within structurally prepared dilatant zones or adjacent to district and regional-scale fault zones. Mineralization also occurs associated with sheeted veins, stockworks, endoskarns, and complex polymictic breccias. In the metamorphosed sedimentary rocks, mineralization occurs associated with dense fracture zones in structurally prepared sites and as stratiform manto-style replacements in reactive carbonate and calcareous siltite and schist units, as well as in cross-cutting breccia veins and dikes.

Field observations, petrographic studies, metallurgical studies, and process mineralogy studies indicate that there were likely multiple stages of mineralization, possibly separated by extended time periods. Early higher temperature, precious metal-rich mineralization with a potential magmatic fluid source was overprinted by younger, lower temperature Au and Sb-Ag mineralization; this was again overprinted by later epithermal mineralization involving meteoric water input into the hydrothermal system with a distinctly different style and geochemical signature.

The gold mineralization at the Hangar Flats and Yellow Pine deposits occurs in intrusive rocks associated with the Atlanta Lobe of the Idaho Batholith. Strong mineralization is localized along an overall north to south striking fault zone and also along northeast striking splay faults and dilatational fault jogs. Dilatant zones have generally provided conduits for movement of mineralizing hydrothermal fluids. Multiple episodes of fracturing have allowed multiple episodes of hydrothermal mineralization.

The gold mineralization at the West End Deposit occurs in metasedimentary rocks intruded by the Idaho Batholith and also within the intrusive rocks. The metasediments occur as pendants and xenoliths within the intrusive rocks. Strong mineralization is localized along a northeast striking fault zone and splay faults that strike northeast and east. Pull-apart fracturing along dilatant northeast fault jogs and splays provided conduits for movement of mineralizing hydrothermal fluids. Multiple episodes of fracturing allowed multiple episodes of hydrothermal mineralization.

Intrusive hosted precious metals mineralization typically occurs in structurally prepared zones in association with very fine-grained disseminated arsenical pyrite (FeS2) and to a lesser extent arsenopyrite (FeAsS). Base metal sulfides are uncommon. Arsenical pyrite is the primary host for gold mineralization, and gold only rarely occurs as discrete particles and, if so, typically only in rare sub-micron size particles, but the vast majority of the gold instead occurs in solid solution within the pyrite crystal lattice. Arsenopyrite is the only other significant gold-bearing sulfide mineral in the intrusive hosted deposits. Base metals (except for arsenic, antimony, and tungsten) are rare and occur at very low concentrations, at or below typical crustal abundance levels. Various oxidized products of the weathering of the primary sulfides are found in the intrusives, including goethite, hematite, jarosite, and scorodite and host precious metal mineralization in the oxidized portions of the deposits.

Antimony mineralization occurs primarily associated with the mineral stibnite (Sb2S3). Other antimony-bearing phases include miargyrite (AgSbS2), gudmundite (FeSbS), chalcostibite (CuSbS2), tetrahedrite [(Cu, Fe)12Sb4S13], and owyheeite [(Pb)10(Ag)3-8(Sb)11-16(S)28]. There is a weak, but persistent association of volumetrically small, typically <0.25%, base metal mineralization associated with the antimony mineralization and includes rare occurrences of chalcopyrite (CuFeS2), galena (PbS), sphalerite (ZnS) and molybdenite (MoS2). Zones of high grade, silver-rich mineralization locally occur with antimony and are related to the presence of pyrargyrite (Ag3SbS3), hessite (Ag2Te) and acanthite (Ag2S).

Tungsten mineralization is typically and essentially exclusively associated with the mineral scheelite (CaWO4). Observations suggest tungsten occurs late in the paragenesis, but precedes the stibnite mineralization since stibnite has been found in numerous past studies cementing veins and brecciated scheelite fragments.

Although mercury mineralization is rare in the area of the three main deposits and in the west side of the district, studies of the mineral occurrences to the east in the Cinnabar district, where mercury was historically produced, indicate the primary mercury-bearing minerals are cinnabar (HgS) and coloradoite (HgTe) and to a lesser extent tiemannite (HgSe) and amalgam (HgAg).

Metasediment-hosted mineralization has a similar sulfide suite and geochemistry, but with higher carbonate content in the gangue and a much more diverse suite of late stage minerals. As in the intrusive-hosted mineralization, gold is associated with very fine-grained arsenical pyrite and is tied up in the pyrite lattice. Rarely, submicron sized native gold occurs as inclusions and along fractures, and may be disseminated in highly fractured zones and may produce locally high grades and a minor nugget effect. Metallurgical test work completed by Midas Gold to date suggests around 20% of the gold in the West End metasediment-hosted mineralization may be particulate in nature, but extremely fine-grained.


Mining Methods

  • Truck & Shovel / Loader

Source: p.18, 342

Summary:

Mining at the Stibnite Gold Project would be accomplished using conventional open pit hard rock mining methods. Mining is planned to deliver 8.05 Mst of ore to the crusher per year (22,050 st/d), with stockpiling by ore type (low antimony sulfide, high antimony sulfide and oxide).

The mine plan developed for the Project incorporates the mining of three primary mineral deposits – Yellow Pine, Hangar Flats, and West End – and re-mining and re-processing of the Historic Tailings.

The Historic Tailings are situated within the footprint of the proposed Main WRSF, and would be re-mined and reprocessed during the first four years of the mine schedule to provide adequate terrain for the WRSF. As the tailings material is currently at a size of 97% passing #40 mesh, it is not anticipated to overwhelm the process plant through the additional throughput. The tailings are currently overlain with 5,752 kst of neutralized spent heap leach ore (commonly referred to as the SODA) that must be removed before the Historic Tailings can be mined. The SODA material is planned to be used in the construction of the TSF starter dam during pre production.


Crushing and Grinding
Source: Source p.23, 378


Processing

  • Flotation
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Pressure oxidation
  • Carbon in leach (CIL)
  • Carbon in pulp (CIP)
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Source: Source p.23, 378

Summary:

The Stibnite Gold Project process plant has been designed to process both sulfide and oxide mineralized material from three deposits (Hangar Flats, Yellow Pine, and West End) as well as Historic Tailings from former milling operations. The design of the processing facility was developed based on the laboratory testing, to treat an average of 22,046 st/d, 365 days per year for a total of 8.05 million tons per year.

ROM material would be crushed and milled, then flotation and hydrometallurgical operations would be used to recover antimony as a stibnite flotation concentrate (with some silver and minor gold), doré bars containing gold and silver, and small quantities of elemental mercury, collected in flasks, to prevent its potential release into the environment. Historic Tailings would be introduced into the ball mill during the first 3 - 4 years of operation.

The processing plant consists of a primary crusher, SAG mill, ball mill, two sequential flotation circuits, a POX circuit, CIP circuit, CIL circuit, and a conventional adsorption desorption-recovery (ADR) plant. The designed process plant processes sulfide material to produce up to two mineral concentrate products: (1) when there is sufficient antimony grade to warrant, an antimony sulfide (stibnite)\ concentrate that would to be filtered, trucked off-site and sold; and, (2) for all material processed, an auriferous sulfide concentrate that would be oxidized onsite via POX, then processed via agitated leach, carbon stripping and refining to produce a gold- and silver-rich doré.

The process plant was designed to process 22,046 st/d through crushing, milling/grinding, flotation and tailings processing operations. Zones in both Yellow Pine (YP) and Hangar Flats (HF) contain sufficient antimony to warrant processing for antimony recovery. The antimony would be recovered as stibnite flotation concentrate and would be shipped off-site for further processing.

Run-of-mine (ROM) material would be crushed and milled, then flotation would be used to recover antimony as a stibnite flotation concentrate (with some silver and minor gold) when there is sufficient antimony to justify it. For all sulfide ore, an auriferous bulk sulfide flotation concentrate would be produced and oxidized in an autoclave. The autoclave residue and flotation tailings would be processed through conventional cyanidation and, doré bars produced containing gold and silver. Historic Tailings would be introduced into the ball mill during the first 3 - 4 years of operation. Tailings from the operation would be deposited in a geomembrane lined TSF. The process operations include the following components:

- Crushing Circuit – ROM material would be dumped onto a grizzly screen and into the crusher dump hopper feeding a jaw crusher operating at an average utilization of 75% yielding an instantaneous designthroughput of 1,225 short tons per hour (st/h).

- Grinding Circuit – The grinding circuit incorporates a single semi-autogenous (SAG) mill, single ball mill design with an average utilization of 92%, yielding an instantaneous design-throughput of 998.5 st/h. When Historic Tailings are processed during early years of the operation, the slurry from the plant would also flow to the cyclone feed pump box. Cyclone underflow flows by gravity to the ball mill; cyclone overflow, at 33% solids with a target size of 80% passing (P80) 75 microns, would be screened to remove tramp oversize and flow through a feed sample system and on to the antimony or gold rougher flotation circuit, depending on the antimony concentration of the material.

- Flotation Circuit (Antimony and Gold) – The flotation circuit consists of up to two sequential flotation stages to produce two different concentrates; the first stage of the circuit was designed to produce an antimony concentrate when the antimony grade is high \ enough, or bypassed if not, and the second stage was designed to produce a gold-rich concentrate.

- Pressure Oxidation Circuit – Two concentrate surge tanks would be pumped to the autoclave feed tank, which would feed the autoclave. The autoclave is designed to provide one hour of retention time at 428 degrees Fahrenheit to oxidize the sulfides and liberate the precious metals. Autoclave discharge would be processed through flash vessels and gas discharge is processed through a scrubber. Slurry discharge from the flash vessels would be processed through the basic ferric sulfate (BFS) re-leach tanks to stabilize the solids prior to cyanide leaching.

- Oxygen Plant – An oxygen plant producing 670 st/d of gas at 95 percent oxygen and a gauge pressure (psig) of 570 is planned. The oxygen would be from a vendor-owned oxygen plant located near the autoclave building providing the autoclave with an “over the fence” supply.

- Oxidized Concentrate Processing – Post-POX, the concentrate stream would be conditioned with lime and leached for 24 hours and discharged to a six stage pump-cell carbon-in-pulp (CIP) circuit for precious metal recovery from this high grade stream. The CIP tailings would be discharged to the flotation tailings leach circuit for extended retention time and to minimize reagent costs for the tailings leach system.

- Oxide Carbon-in-Leach and Tailings Detoxification – A (CIL) circuit was included in the design of the process plant to recover gold from non-refractory material in the flotation tailings, and in oxide material from the West End deposits that would be processed during oxidation circuit scheduled maintenance periods.

- Carbon Handling – Loaded carbon from the CIP circuit would be processed through a conventional carbon handling circuit.

- Gold Room – Precious metals would be recovered from the strip solution by electrowinning.

- Tailings – Tailings would be pumped from the process plant to the TSF In a HDPE-lined carbon steel pipe.

- Process Control Systems - The process plant design includes an integrated process control system.

Recoveries & Grades:

CommodityParameterAvg. LOM
Gold Head Grade, oz/ton 0.05
Silver Head Grade, oz/ton 0.07
Antimony Head Grade, % 0.07

Projected Production:

CommodityProductUnitsLOM
Gold Metal in concentrate koz 3.2
Gold Metal in doré koz 4,002
Silver Metal in concentrate koz 382
Silver Metal koz 1,085
Antimony Concentrate k tons 85
Antimony Metal in concentrate k lbs 67,900

Operational Metrics:

Metrics
Daily mining capacity 22,050 tons of ore *
Daily milling capacity 22,050 tons of ore *
Annual mining capacity 8.05 M tons of ore *
Waste tonnes, LOM 346,910 k tons *
Ore tonnes mined, LOM 98,066 k tons *
Total tonnes mined, LOM 436,060 k tons *
Annual milling capacity 8.05 M tons of ore *
Tonnes processed, LOM 98,066 k tons *
* According to 2014 study.

Reserves at February 15, 2018:

CategoryTonnage CommodityGradeContained Metal
Measured 4,623 kt Gold 2.53 g/t 377 koz
Measured 4,623 kt Silver 3.91 g/t 581 koz
Measured 4,623 kt Antimony 0.25 % 25,821 k lbs
Indicated 100,289 kt Gold 1.62 g/t 5,234 koz
Indicated 100,289 kt Silver 2.47 g/t 7,955 koz
Indicated 100,289 kt Antimony 0.08 % 178,016 k lbs
Measured & Indicated 104,912 kt Gold 1.66 g/t 5,610 koz
Measured & Indicated 104,912 kt Silver 2.53 g/t 8,536 koz
Measured & Indicated 104,912 kt Antimony 0.09 % 203,838 k lbs
Inferred 23,174 kt Gold 1.29 g/t 959 koz
Inferred 23,174 kt Silver 2.04 g/t 1,518 koz
Inferred 23,174 kt Antimony 0.04 g/t 20,524 k lbs

Commodity Production Costs:

CommodityUnitsAverage
Credits (by-product) Gold USD -85 / oz *
Cash costs Gold USD 653 / oz *
Cash costs Gold USD 568 / oz *†
Total cash costs Gold USD 597 / oz *†
All-in sustaining costs (AISC) Gold USD 616 / oz *†
All-in costs Gold USD 872 / oz *†
Assumed price Silver USD 22.5 / oz *
Assumed price Gold USD 1,350 / oz *
* According to 2014 study / presentation.
† Net of By-Product.

Operating Costs:

Units2014
OP mining costs ($/ton mined) USD 2 *
OP mining costs ($/ton milled) USD 9.08 *
Processing costs ($/ton milled) USD 14.5 *
Total operating costs ($/ton milled) USD 26.7 *
* According to 2014 study.

2014 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Initial CapEx $M USD 970.3
Sustaining CapEx $M USD 154.4
Total CapEx $M USD 1,125
OP OpEx $M USD 890
Processing OpEx $M USD 1,417
G&A costs $M USD 306.9
Total OpEx $M USD 2,614
Total Taxes $M USD 415.3
Royalty payments $M USD 91.8
Net revenue (LOM) $M USD 5,722
Net Operating Income (LOM) $M USD 3,039
Net Income (LOM) $M USD 1,499
Pre-tax Cash Flow (LOM) $M USD 1,915
After-tax Cash Flow (LOM) $M USD 1,499
Pre-tax NPV @ 0% $M USD 1,915
Pre-tax NPV @ 5% $M USD 1,093
Pre-tax NPV @ 10% $M USD 589.7
After-tax NPV @ 0% $M USD 1,499
After-tax NPV @ 5% $M USD 831.8
After-tax NPV @ 10% $M USD 418.4
Pre-tax IRR, % 22
After-tax IRR, % 19.3
Pre-tax payback period, years 3.2
After-tax payback period, years 3.4

Proposed Heavy Mobile Equipment as of December 8, 2014:
Source: Source p.358
HME TypeModelQuantity
Dozer Caterpillar D6TLGP 1
Dozer (crawler) Caterpillar D10 5
Drill Caterpillar MD6290 5
Drill Caterpillar MD5150 2
Excavator Caterpillar 349 2
Grader Caterpillar 16M 3
Loader Caterpillar 994 4
Loader Caterpillar 990 1
Truck (haul) Caterpillar 740 5
Truck (haul) Caterpillar 789 18
Truck (water) Caterpillar 777 2

Mine Management:

Job TitleNameProfileRef. Date
VP, Project Development John Meyer LinkedIn Dec 20, 2019


Corporate Filings & Presentations:

DocumentYear
Press Release 2018
Pre-Feasibility Study Report 2014

News:

NewsDate
Midas Gold Completes Positive Feasibility Study for the Stibnite Gold Project, Idaho December 22, 2020
Midas Gold Corp.: Federal Permitting Dashboard to Improve Coordination for the Stibnite Gold Project September 10, 2020
Draft EIS on Midas Gold's Stibnite Gold Project Set for Release July 2, 2020
Midas Gold Completes US$35.0 Million (C$47.6 Million) Financing March 17, 2020
Midas Gold Announces Private Placement Re-Pricing March 10, 2020
Midas Gold Announces US$35 Million Private Placement February 27, 2020
Permitting Process for Midas Gold’s Stibnite Gold Project Continues to Advance October 7, 2019
Midas Gold Continues to Advance Solutions to Address Pre-existing Contamination in the Stibnite Mining District August 9, 2019
Midas Gold Corp. Announces Closing of C$19.9 Million Bought Deal Public Offering: Funds to be used to advance the Stibnite Gold Project, Idaho June 19, 2019
Midas Gold Corp. Announces Bought Deal Public Offering June 10, 2019
State & Federal Agencies Update Permitting Schedule for Midas Gold’s Stibnite Gold Project April 2, 2019
State & Federal Agencies Update Permitting Schedule for Midas Gold’s Stibnite Gold Project January 29, 2019
State & Federal Agencies Update Permitting Schedule for Midas Gold’s Stibnite Gold Project July 3, 2018

Aerial view:

Terms of Use Privacy Policy © 2020 MDO Data Online Inc.