The Soledad Mountain Mine (the “Mine”) is a gold-silver mine located is located 5 miles south of the town of Mojave in Kern County, southern California. The Mine uses conventional open pit mining methods and the cyanide heap leach and Merrill-Crowe processes to recover gold and silver from crushed, agglomerated ore.
Gold and silver production is projected to average approximately 74k oz and 781k oz respectively per year although this is expected to fluctuate from year to year depending upon the ore head grades. Gold and silver production is projected to be 807k oz of gold and 8.3MM oz of silver over a period of ~11 years. ✲
Access to site is from State Route 14 and an existing paved County road. A power line crosses the property boundary and the Union-Pacific railroad lines parallel State Route 14 within ~1 mile of the Mine. The primary water supply for the Mine is also located within a mile of site.
Highlights of the February 2015 feasibility study, calculated on 100% basis, include: ✲
- Life-of-mine average annual gold production of 74k oz and silver production of 781k oz during full production Years 2-11;
- First quartile total cash costs net of by-products of US$518/oz of gold (including royalties, California fees, property taxes, off-site refining charges and reclamation financial assurance) and of US$558/oz of gold including sustaining capital costs;
- 11-yr mine life;
- After-tax net present value of US$214MM (5% discount rate);**
- After-tax internal rate of return of 28.3%;**
- Utilization of a high-pressure grinding roll (the “HPGR”) to size and prepare ore particles for heap leaching (see below for benefits) and
- Strong project economics with only 65% of the resource included in the feasibility study
*Base case gold price of US$1250/oz and silver price of US$17.00/oz
** Net of $25.4MM of capital expenditures spent prior to December 31, 2014
The primary ore types that will be mined are rhyolite porphyry and flow-banded rhyolite, pyroclastics and quartz latite porphyry representing approximately 70%, 10% and 20% of the ore tonnage respectively. Minor quantities of siliceous vein material (0.1%) will also be mined. The rock types will be found in different areas and at various stages of the mine life. The primary rock types are of extrusive volcanic origin and are quite similar in chemical composition and are high in silica with little or no clay.
The crushing-screening plant includes a primary and secondary crusher and screen in closed circuit with the secondary crusher. The HPGR is used as part of the crushing-screening circuit to prepare the ore particles for stacking on the two leach pads.
The HPGR consists of two counter-rotating rolls - one fixed roll and a ‘floating’ roll. The ‘floating’ roll is mounted on and can move freely on two slides and the grinding forces are applied by four hydraulic rams. Ore is choke-fed to the gap between the rolls.
Assessments carried out by two HPGR manufacturers, third party technical consultants, and Company management have indicated that benefits of using the HPGR could include:
- Higher gold and silver recoveries due to the formation of micro-cracks in ore particles;
- Faster gold and silver extraction rates;
- Stronger agglomerates due to a more favorable overall particle size distribution and this will also impact the flow rate of solutions through the heap;
- Lower capital costs than a four-stage, conventional crushing-screening plant;
- Manageable dust control with fewer transfer points;
- Lower energy consumption and thus lower operating costs and
- Circuit flexibility that will readily permit future upgrades such as a finer HPGR feed size or the recycle of edge product
✲ This is forward-looking information and includes risks and assumptions. Click here to see our statement on forward-looking information.