Gold and Silver in Querétaro, Mexico
The flagship property of Starcore International Mines is the San Martin gold and silver mine. The mine has been in operation since 1993 at 350tpd and currently operates at 850tpd. The mine was acquired by Starcore in February of 2008 from Goldcorp who had acquired the asset through the takeover of Wheaton River. The mine is an underground epithermal deposit with gold quartz based limestone and has an average gold grade of 2.31 grams and 18 grams of silver ( NI 43-101 2014 Dave Gunning, Joe Campbell). The historical production of the mine is over half a million ounces and the mine sits on 100% owned claim package of 12,992 hectares, which offers the upside of exploration and the possibility of discovering the source of the current mineralization.
The San Martin project is located 50 km east of the City of Querétaro in Querétaro State, and about 250km northwest of Mexico City. The city of Queretaro boasts a population of over 1 million people and is one of the safest states in Mexico. Major companies such as Bombardier Aerospace, Safran, Eurocopter, and Canada’s Héroux-Dvetek all have operations in Queretaro.
In 1982, the area of San Martin was declared a National Reserve; however, by 1986, Luismin (previous owner) had reached an agreement to conduct exploration/exploitation in the area. Mining began in 1993 at 300 tpd and the production increased on a yearly basis to the present rate of 747 tpd with the capacity of 900 tpd.
High grade mineralization was discovered at San Martin in the 18th Century, and is reported to have been mined over a period of 40 years; however, no production records exist. Between 1900 and 1924, an estimated 250,000 tonnes grading 15 g Au/t and 100 g Ag/t was reportedly mined. Mineralization occurs in Upper Cretaceous black limestone and calcareous shales of the Soyatal Mexcala Formation as electrum, and silver selenide minerals principally associated with quartz and to a lesser degree with calcite. The deposit is an epithermal, probably high sulphidation precious metal (Ag-Au) type (metal ratio Au:Ag at 1:10), related to a Tertiary dacitic/andesitic intrusive dome.
Mineralization is generally made up of breccia that commonly is concordant with a limestone/shale contact (in the San Martin and San Jose areas) which forms the relatively steeply dipping tronco deposits, these troncos contact the younger volcanic flows (dacite and ignimbrite) where they have formed the more horizontal manto portions of the deposit. The mineralized economic breccia grades from 30 g Ag/t to 250 g Ag/t. Exploration has been concentrated along the NE trending breccia zone however evidence of a northerly trend in area 30 leads us to suspect possible other structures together with 2.0 g Au/t to 30 g Au/t over widths that vary from 1.0 to 17.0 m but average 4.0 m.
San Martin 3D mine model
At depth in the San Martin area the Guadalupe vein was found in late 2007. This vein is sub parallel with the San Martin segment is narrower, more vein like and somewhat higher grade than the San Martin structure at the same elevation. Drilling and lateral development are being used to prove reserves in this vein which indicates the potential for other similar structures.
Discovered in late 2007, this vein is a sub-parallel vein to San Martin located below level 8. Drilling and lateral development are being used to prove reserves in this area which indicates the potential for other similar structures.
Discovered in 2009, the SAM Vein was encountered on level 5 & 6 in Area 29. This vein is further west than previous ore bodies and may have been deposited along an unconformity in limestone, it strikes north where it has now been found in contact with the area 30 fault and dips up to the west.
Discovered in 2011 the western fault offset of Pilotos ore body and mined for a year at 3,000-5,000 tons per month with grades of 5-20 g/t. This area is limited in a real extent by faulted volcanic rocks and mining has now extracted most of these deposits with only small pillars remaining.
San Martin Footwall
Discovered in 2012 this area has been found to host several veins 1 - 5m thick generally dipping 20 degrees to the east and striking north/south. It has been found within 50 meters of main in the footwall of San Martin structure in the footwall which was previously thought to be exclusively shales. To date at least 4 veins have been found above level 4 in the northeast of San Martin and possibly 2 veins above level 2 further south. Some of the veins are vertical and some are dipping around 40 degrees. In general most are striking parallel to San Martin breccia.
Proven and Probable Reserves for the San Martin Mines (NI 43-101 Technical Report- Filed October 22, 2014)
Starcore International Mines Ltd. has released results for a recently completed reserve estimate for its San Martin mine in Queretaro, Mexico.
The result of the estimate, effective as of July 31, 2014, is proven and probable reserves totaling 486,586 tonnes at a grade of 2.31 grams per tonne gold and 18.5 grams per tonne silver. In addition to the proven and probable reserves, an inferred mineral resource is estimated at 898,000 tonnes at an approximate grade of 2.15 grams per tonne gold and 24 grams per tonne silver. Inferred mineral resources are not known to the same degree of certainty as mineral reserves and do not have demonstrated economic viability.
- The reserve estimate is based on the methods used for the last 14 years by Luismin, Goldcorp and Starcore at the mine, and modified over the past few years to try to account for changes in dilution due to the increased reliance on Tronco narrower vein-hosted ores.
- Total operating costs of $74 (U.S.) per metric tonne at a gold price of $1,250 (U.S.) and silver price of $19.23 (U.S.);
- Metal recoveries of 86 per cent for gold and 52 per cent for silver;
- Resultant cut-off grade of 2.2 grams per tonne gold equivalent (compared with two grams in the prior year);
- Mining dilution of between 10 per cent and 30 per cent depending on the structure;
- Specific gravity of 2.6.
Reserves and Resources for the San Martin Mine July 31, 2014
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San Martin Mine
Inferred Mineral Resources are not known to the same degree of certainty as Mineral Reserves and do not have demonstrated economic viability. A 65:1 silver to gold equivalency ratio was used to calculate gold equivalent ounces. The reserves above exclude approximately 20,300 equivalent ounces of metal contained in carbonaceous limestone discussed in MD&A April 30, 2015. Dave Gunning, P. Eng is the qualified person. As of July 31, 2014, reserves and resources at San Martin as reported in “RESERVES AND RESOURCES IN THE SAN MARTIN MINE, MEXICO AS OF JULY 31, 2014”, dated October 6, 2014, prepared by Joseph Campbell, P. Eng. (the “Technical Report”), as filed on SEDAR and available on the Company website
The ratio of probable to proven reserve tonnage is roughly 1.7:1, and in total there are 40,600 contained gold-equivalent ounces (using a 65:1 equivalency factor). The previous reserve estimate at San Martin was compiled as of July 31, 2013, and totaled 705,998 tonnes at 2.53 grams per tonne gold and 23.6 grams per tonne silver (containing 66,520 equivalent ounces of gold). San Martin milled 308,610 tons since the last resource estimate at an average grade of 2.55 grams per tonne gold and 24.2 grams per tonne silver. The proven and probable reserves outlined above are adequate for 1.5 additional years of production.
David Gunning, PEng, a director of the company and chief operating officer, is the company’s qualified person on the project as required under NI 43-101, and has prepared the technical information contained in the website that has been reviewed by Mr. Campbell.