Mining Intelligence and News
United States

Soledad Mountain Mine

Click for more information

Categories

Overview

Mine TypeOpen Pit
StatusActive
Commodities
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Production Start... Lock
Mine Life... Lock
SnapshotAt the Soledad Mountain gold and silver are extracted from mineralized material by heap leaching. In addition, Golden Queen produces aggregate for construction and landscaping needs at the Soledad Mountain.

The fire incident at the secondary crusher occurred on December 14, 2023. The secondary crusher was down for approximately 6 weeks that delayed the stacking of new ore on the pad. The Golden Queen expects lower production in the first quarter of 2024 due to the fire; however, Golden Queen’s 2024 production is not anticipated to be materially affected.

Owners

SourceSource
CompanyInterestOwnership
Andean Precious Metals Corp. 100 % Indirect
Andean Precious Metals Corp. completed the acquisition of a 100% interest in Golden Queen Mining Company LLC which principal asset is the Soledad Mountain mine and heap leach operation.

Contractors

Lock

- subscription is required.

Deposit type

  • Vein / narrow vein
  • Epithermal
  • Volcanic hosted

Summary:

Deposit Types
The Soledad Mountain gold-silver deposit is best interpreted as a volcanic rock-hosted, low sulfidation, epithermal vein system of the low base metal type. Individual major veins formed by episodic deposition of quartz, adularia, sericite, calcite, and sparse sulfide minerals in open faults and fractures, coeval with adjacent sheeted and quartz-vein stockwork zones and quartz ±adularia ±sericite alteration of nearby wall-rocks. Other examples of this deposit class include districts such as Oatman (Arizona), Bullfrog (Nevada), Bodie (California), and Tayoltita (Mexico). Soledad Mountain contains an unusually large number of individual veins within a relatively small area by comparison to the examples cited. Post-mineral faulting at Soledad Mountain has extensively sheared and brecciated the veins, most likely due to mid-Miocene to present-day wrench-fault tectonism between the nearby San Andreas and Garlock fault systems.

Mineralization
Gold and silver mineralization occurs in a swarm of mainly northwest-striking, subparallel to anastomosing, low-sulfidation, epithermal quartz veins that formed in faults and fractures within the Miocene rhyolitic volcanic units. Veins occur in parallel and, locally, en echelon patterns over a total strike-length of 7,000 ft and a total width of 4,500 ft. The veins have been sheared and brecciated to varying degrees by post-mineral faulting.

More than 20 gold-silver veins and related vein splits occur at Soledad Mountain. Veins generally strike N40°W and dip at moderate to high angles to the northeast and to the southwest.

Mineralization consists of fine-grained pyrite, covellite, chalcocite, tetrahedrite, acanthite, native silver, pyrargyrite, polybasite, native gold, and electrum within discrete quartz veins, veinlets, veinlet stockworks and irregular zones of silicification. Gangue minerals include quartz, potassium feldspar (adularia), ferruginous kaolinitic clay, sericite, hematite, magnetite, goethite, and limonite. As stated by Bruff (1998, July) “At least five generations of quartz veining have been identified in hand-specimens within the major fissure-fill veins.” Calcite has also been reported by Diblee (1963) and in GQMC logging, as well as calcite replacement textures in quartz. Rhythmically banded veins are quite likely to show alternating layers of quartz and adularia (Bruff, 1998, July).

The veins formed by intense alteration of volcanic rocks and by deposition of quartz and sericite rich material in fault and fracture zones. The alteration and veins are generally low in sulfur, with total sulfide content generally being 1% or less. Vein “zones” consist of one or more central veins surrounded by either a stockwork or parallel zones of sheeted, narrow quartz veins. The effect is to have a core vein of 1 ft to 20 ft in width (with gold grades being generally greater than 0.1 oz/ton), surrounded by lower grade mineralization in the adjacent quartz-vein stockwork and sheeted vein zones. The widths of the stockwork and sheeted vein zones vary from 5 ft to 150 ft.

Native gold and electrum are generally associated with siliceous gangue and occur as particles with diameters ranging from less than 10 µm to as much as 150 µm or more. Electrum contains about 25% silver. Gold grades greater than 0.1 oz/ton appear to occur where veins exhibit multiple generations of quartz, adularia and sericite. Sheeted veins and stockwork veinlets decrease in grade laterally outward from the core veins. Silver to gold ratios vary from 1:1 in shallow portions of veins in the south half of the deposit to greater than 35:1 at deeper levels (600 Level) in the north half of the deposit. Silver to gold ratios increase generally with depth, averaging about 10:1 at the surface of the Golden Queen vein, to about 35:1 at the 600 Level in the same vein. There is also a general horizontal zonation, from relatively silver-rich in the northeastern vein systems (e.g., Queen Esther – Independence), to gold-rich structures in the southwest (e.g., the Sheeted Vein system). The district silver-to-gold ratio average ranges from 15:1 to 18:1.

Alteration within mineralized zones consists of fracture-controlled and disseminated fine-grained silica, adularia, sericite, and minor pyrite. Intense quartz-feldspar-sericite alteration reportedly occurs in zones from about 10 ft to over 150 ft wide. Volcanic rocks are weakly silicified and argillically altered between and adjacent to zones of strong silicification. Weakly silicified and argillically altered rocks grade laterally into weakly to strongly propyllitized + illitized volcanic rocks. Propylitic alteration is best developed in the quartz latite flows.

Important vein systems, from the northeast to southwest, are the Black, Reymert, Karma-Ajax, Independent, Queen Esther, Silver Queen, No. 1 Footwall, Golden Queen - Starlight, Soledad, Alphason, Gypsy, Echo, Hope, Elephant, Bobtail, Excelsior, and McLaughlin. Post-mineral offset of about 300 ft on the east-dipping, apparently listric, Main Fault has displaced the Starlight vein in the footwall, from its upper continuation known as the Golden Queen vein in the hanging wall. Portions of the Soledad and No. 1 Footwall veins are also displaced by offset on the Main Fault. Veins northeast of the Golden Queen vein dip from 40° to 70° northeast. Veins southwest of the Golden Queen Vein dip about 70° southwest.

A zone of “Flat Ore” is present between the Starlight and Silver Queen Vein, in the hanging wall of the Main Fault. Flat Ore is a complex zone of veins and stockwork mineralization that is from 100 ft to 125 ft thick and nearly horizontal that at least in part consists of blocks of the mineralized zones cut by the Main Fault. Individual, parallel and en-echelon vein systems are present over a total strike length of 7,000 ft trending northwest, and a total width of 4,500 ft. Veins and vein zones are from 5 ft to 150 ft in thickness, 325 ft to 3,000 ft long, and from 300 ft to 1,000 ft in extent along dip. The horizontal distance between individual veins is from 50 ft to greater than 400 ft.

Reserves

Lock

- subscription is required.

Mining Methods

Lock

- subscription is required.

Comminution

Crushers and Mills

Lock

- subscription is required.

Processing

Lock

- subscription is required.

Production

Operating results have not been publicly available since May 22, 2019, until the fourth quarter of 2023 due to the transfer of ownership of Soledad Mountain to Andean Precious.

Production numbers of products for the full 2023 year are calculated from the production amounts for the fourth quarter of 2023. The Q4 2023 production amounts are as follows:
- Metal in doré Gold: 18,375 oz
- Metal in doré Silver: 216,839 oz
- Metal in doré Gold Equivalent: 18,497 oz.
CommodityUnits20242023201820172016
Gold Equivalent oz  ....  Subscribe  ....  Subscribe
Gold oz  ....  Subscribe42,28246,19919,030
Silver oz  ....  Subscribe393,007239,141194,792
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.

Operational metrics

Metrics202420232022202120202019201820172016
Total tonnes mined  ....  Subscribe8,860 k tons
Tonnes processed  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe4,119,262 tons3.52 M tons3.55 M tons2,666 k tons
Daily processing capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Hourly processing rate  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe772 tons669 tons649 tons703 tons
Stripping / waste ratio  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe2.9 3.9 2.4
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe4.51 M tons3.76 M tons2,578 k tons
Waste  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe13 M tons14.5 M tons6,282 k tons
Daily processing rate  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe7,410 tons
^ Guidance / Forecast.

Production Costs

CommodityUnits2024202320182017
Credits (by-product) Gold USD
Total cash costs (sold) Gold USD
Total cash costs Gold Equivalent USD  ....  Subscribe  ....  Subscribe
Total cash costs (sold) Gold Equivalent USD  ....  Subscribe
Total cash costs Gold USD 997 / oz **   1,136 / oz **  
Total cash costs (sold) Gold USD 998 / oz **   1,140 / oz **  
All-in sustaining costs (sold) Gold Equivalent USD  ....  Subscribe  ....  Subscribe
All-in sustaining costs (AISC) Gold USD 1,215 / oz **   1,556 / oz **  
All-in costs Gold Equivalent USD  ....  Subscribe
^ Guidance / Forecast.
** Net of By-Product.

Operating Costs

Currency20182017
Total operating costs ($/t milled) USD  ....  Subscribe  ....  Subscribe

Financials

Units202420182017
Capital expenditures (planned) M USD  ....  Subscribe
Revenue M USD 58.4   62.1  
Operating Income M USD 4.1   -6.1  

Heavy Mobile Equipment

Lock

- subscription is required.

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Apr 26, 2024
....................... Subscription required ....................... Subscription required Subscription required Jan 12, 2024
....................... Subscription required ....................... Subscription required Subscription required Jan 12, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 26, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 26, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 26, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 26, 2024

EmployeesContractorsTotal WorkforceYear
...... Subscription required ...... Subscription required ...... Subscription required 2023
...... Subscription required 2022
...... Subscription required 2021
...... Subscription required 2020
...... Subscription required 2019
...... Subscription required 2018
...... Subscription required 2017
...... Subscription required 2016

Aerial view:

Lock

- subscription is required.