The San Francisco mine was previously developed and operated by Geomaque from 1995 through 2000. Time during which approximately 13.5 million tonnes of ore at a grade of 1.13 g/t gold were treated by heap leaching, and 300,834 oz of gold were recovered. Metal recovery from the pregnant solution was effectuated through carbon columns. Loaded carbon from the columns was transferred to a Zadra elution plant for precious metal extraction and the production of Doré bullion. Average gold recovery over the mine life was about 63%. Mining operations ceased in 2001 as a result of low gold prices, although leaching and rinsing of the heap continued for approximately one year after this.
In 2005 Timmins Gold entered into an agreement to fully acquire the mine and processing equipment. On March 31, 2008, both Micon International Limited (an independent mineral engineering firm), and Independent Mining Consultants, Inc. (an independent mineral engineering firm), produced an independent pre-feasibility study on the San Francisco Mine, later updated in January 2009. The study recommended development and re-commissioning of the mine; concluding that it was an advanced-stage exploration project with significant economic potential.
The following table sets out the Mineral Reserves of the San Francisco mine outlined through the conclusion made by Micon in that report.
| Case | Reserve Class | Cut-off Grade (g/t gold) |
Reserve (000 t) |
Grade (g/t gold) |
Gold (000 oz) |
|---|---|---|---|---|---|
| High Grade Crusher feed | Probable | 0.5 | 12,000 | 1.05 | 403.7 |
| Low Grade Crusher feed | Probable | 0.23 | 4,653 | 0.88 | 132.0 |
| Sub-total Crusher feed | Probable | 16,653 | 1.01 | 535.7 | |
| Low Grade ROM leach | Probable | 0.28 | 5,981 | 0.39 | 75.3 |
| Grand Total | Probable | 22,634 | 0.84 | 611.0 |
Following Micon’s encouraging findings from the technical prefeasibility study on San Francisco, Timmins Gold began commercial operations in April of 2010. Since then, the mine has processed more than 1.2 M ounces of gold and becoming one of the most successful mining operations in terms of economic performance and operational results.
The following table shows operating performance annually.
| Processed Gold (Oz) | Gold Sold (Oz) | Annual Real Recovery | |
|---|---|---|---|
| 20101 | 86,054 | 46,090 | 53.6% |
| FY-2011 | 137,455 | 72,507 | 52.7% |
| FY-2012 | 150,007 | 94,445 | 63.0% |
| FY-2013 | 197,334 | 119,657 | 60.6% |
| FY-2014 | 171,421 | 120,027 | 70.0% |
| FY-2015 | 138,031 | 93,198 | 67.5% |
| FY-2016 | 142,516 | 100,324 | 70.4% |
| FY-2017 | 109,202 | 83,557 | 76.5% |
| FY-2018 | 92,984 | 51,387 | 55.3% |
| FY-2019 | 51,113 | 36,344 | 71.1% |
| Q1, 2020 | 5,224 | ||
| 1,276,117 | 822,760 | 64.5% |
1 Excludes first quarter