Economic Studies
Ixtaca: One of Mexico’s Premier Precious Metal Discoveries
Almaden has produced a Feasibility Study (“FS”), a Pre-Feasibility Study and three Preliminary Economic Assessments (“PEAs”) on the Ixtaca deposit since April 2014.
These Economic Studies reflect our advancing engineering work on the project, the changing metals price environment, our interaction with local communities, and the opportunities we have capitalized on during depressed metals markets, such as the option agreement on the Rock Creek Mill.
In December 2018, Almaden announced the results of its FS on the Ixtaca deposit, a brief overview of which is posted below, along with links to the news release.
2018 Feasibility Study ("FS")
On December 11, 2018, Almaden announced positive results of the independent FS prepared in accordance with National Instrument 43-101 (“NI 43-101”) for the Ixtaca precious metals deposit, located in Puebla State, Mexico.
Highlights
(all values shown are in $US; base case uses $1275/oz gold and $17/oz silver prices, and equivalency calculations assume 75:1 silver:gold ratio):
Average annual production of 108,500 ounces gold and 7.06 million ounces silver (203,000 gold equivalent ounces, or 15.2 million silver equivalent ounces) over first 6 years
After-tax NPV(5%) of $310 million and internal rate of return of 41%;
After-tax IRR of 42% and after-tax payback period of 1.9 years
After-tax NPV of $310 million at a 5% discount rate
Initial Capital of $174 million
Average annual production over the first 9 years of 88,780 ounces gold and 5.47 million ounces silver (168,100 gold equivalent ounces, or 11.6 million silver equivalent ounces)
Conventional open pit mining with a Proven and Probable Mineral Reserve of 1.39 million ounces of gold and 85.2 million ounces of silver (See Table 3)
Pre-concentration uses ore sorting to produce a total of 48 million tonnes of mill feed averaging 0.77 g/t gold and 47.9 g/t silver (2.03 g/t gold equivalent over first 6 years, 1.41 g/t gold equivalent over life of mine)
Average LOM annual production of 90,800 ounces gold and 6.14 million ounces silver (173,000 gold equivalent ounces, or 12.9 million silver equivalent ounces)
Operating cost $716 per gold equivalent ounce, or $9.55 per silver equivalent ounce
All-in Sustaining Costs (“AISC”), including operating costs, sustaining capital, expansion capital, private and public royalties, refining and transport of $850 per gold equivalent ounce, or $11.30 per silver equivalent ounce
Elimination of tailings dam by using filtered tailings significantly reduces the project footprint and water usage
Mining under the proposed production plan
The Ixtaca gold-silver project is planned as a typical open pit mining operation using contractor mining. Initial production will ramp up to a mill feed rate of 7,650 tonnes per day followed by an expansion to 15,300 tonnes per day from Year 5 onwards.
An ore control system is planned to provide field control for the loading equipment to selectively mine ore grade material separately from the waste.
Mining operations will be based on 365 operating days per year with three 8 hour shifts per day.
Processing
The Study reflects the Rock Creek process plant which has been purchased by Almaden. Run of mine ore will be crushed in a three-stage crushing circuit to -9 mm.
The Study also incorporates ore sorting, test work for which has shown the ability to separate barren or low grade limestone host rock encountered within the vein swarm from vein and veined material (see Almaden news release of July 16th 2018). Product from the secondary crusher will be screened in to coarse (+20mm), mid-size (12 to 20 mm), and fine (-12mm) fractions. Coarse and mid-size ore will be sorted by an XRT ore sort machine to eject waste rock. Fine ore will bypass the ore sorting and is sent directly to the mill.
Ore sort waste from Limestone and Black Shale is below waste/ore cutoff grade and is placed in the waste rock dump. Ore sort ‘waste’ from the Volcanic unit is low grade ore and will be stockpiled for processing later in the mine life. Ore sorting pre-concentration increases the mill feed gold and silver grades by 32% and 31% respectively compared to run of mine (ROM) grades. The table below shows ROM grades with ore sort waste removed from the ROM, and the resulting mill feed.
Crushed ore is transported to the grinding circuit by an over land conveyor. Grinding to 75 microns is carried out with ball milling in a closed circuit with cyclones. Cyclone underflow is screened and the screen undersize is treated in semi-batch centrifugal gravity separators to produce a gravity concentrate.
The gravity concentrate will be treated in an intensive leach unit with gold and silver recovered from electrowinning cells.
The cyclone overflow will be treated in a flotation unit to produce a flotation concentrate. After regrinding the flotation concentrate leaching will be carried out in 2 stages. CIL leaching for 24 hours will complete gold extraction, followed by agitated tank leaching to complete silver leaching. A carbon desorption process will recover gold and silver from the CIL loaded carbon, and a Merrill Crowe process will recover gold and silver from pregnant solution from the agitated leach circuit.
Cyanide destruction on leach residue is carried out using the SO2/Air process. Final tailings are thickened and filtered then dry stacked and co-disposed with mine waste rock.
Average process recoveries from mill feed to final product over the life of mine are summarized in Table 4 for each ore type.
Water and Waste Management
One of Almaden’s top priorities at Ixtaca is water quality and a mine plan that provides a permanent and consistent long-term supply of water for residents. The plan outlined in the Study has evolved through the open dialogue between the Company and residents over the past number of years and as part of the Social Investment Plan consultation. Please visit our Community page for more information +
Rainfall in the Ixtaca vicinity falls primarily during a relatively short rainy season. With no local water storage facilities, the flash flows of water are currently lost to the communities. Under the Study, rainwater will be captured during the rainy season in the water storage reservoir and slowly released during the dry season, for use by both the mining operation and local residents.
Extensive geochemical studies have evaluated the potential for acid rock drainage and metal leaching from the waste rock and tailings using globally accepted standardised methods of laboratory testing and in compliance with Mexican regulations. Most of the waste rock at Ixtaca is limestone, and the studies of both waste rock and tailings have consistently shown that there is more than enough neutralising potential present in the waste rock to neutralise any acid generated.
Testing to date also indicates low potential for metal leaching. These results along with the excellent access to potential markets in the growing industrial state of Puebla, indicate the potential for rock waste and tailings from the Ixtaca deposit to be secondary resources such as aggregate and cement feedstock. These opportunities will be fully examined in 2019 as part of the Company’s commitment to best sustainable practices.
In consideration of these findings and the hydrologic conditions at Ixtaca, Almaden and its consultants reviewed Best Available Technology and Best Applicable Practice in the design and planning of tailings management at Ixtaca, which resulted in selecting a dry-stack tailings facility which would include co-disposal of waste with filtered tailings, use much less water than traditional slurry facilities, reduce the mine footprint, allow for better dust control, and enable earlier rehabilitation of the tailings and waste disposal areas.
Mineral Reserve Estimate
Mineral Reserves outlined in the table below have been developed by MMTS with an effective date of November 30, 2018, and are classified using the 2014 CIM Definition Standards. The Mineral Reserves are based on an engineered open pit mine plan.
1. Mineral Reserves have an effective date of November 30, 2018. The qualified person responsible for the Mineral Reserves is Jesse Aarsen, P.Eng of Moose Mountain Technical Services (“MMTS”).
2. The cut-off grade used for ore/waste determination is NSR>=$14/t
3. All Mineral Reserves in this table are Proven and Probable Mineral Reserves. The Mineral Reserves are not in addition to the Mineral Resources but are a subset thereof. All Mineral Reserves stated above account for mining loss and dilution.
4. Associated metallurgical recoveries (gold and silver, respectively) have been estimated as 90% and 90% for limestone, 50% and 90% for volcanic, 50% and 90% for black shale.
5. Reserves are based on a US$1,300/oz gold price, US$17/oz silver price and an exchange rate of US$1.00:MXP20.00.
6. Reserves are converted from resources through the process of pit optimization, pit design, production schedule and supported by a positive cash flow model.
Rounding as required by reporting guidelines may result in summation differences.
Capital and Operating Costs
Initial capital cost for the Ixtaca gold-silver project is $174 million and sustaining capital (including expansion capital) is $111 million over the LOM. The estimated expansion capital of $64.5 million will be funded from cashflow in Year 4 for the throughput ramp-up in Year 5. Estimated LOM operating costs are $26.8 per tonne mill feed. The following tables summarize the cost components:
Economic Results and Sensitivities
A summary of financial outcomes comparing base case metal prices to alternative metal price conditions are presented below. The FS base case prices are derived from current common peer usage, while the alternate cases consider the project’s economic outcomes at varying prices witnessed at some point over the three years prior to this study.
This FS and our historic economic studies are or will available on SEDAR or can be viewed in Technical Reports +