Riverside Resources Inc. (“Riverside” or the “Company”) (TSX-V: RRI) and its partner, Sierra Madre Developments (“Sierra Madre”; TSX-V: SMG) provide an update on progress at the 350 km² Peñoles Project in Durango, Mexico. Riverside continues to have a strong cash position with $9,000,000 and major partners funding exploration work in Canada and Mexico. The Company is pleased with progress at its Peñoles project where a partially defined oxide gold prospect (referred to as El Capitan), two historic silver mines that have never been systematically drill tested (Jesus Maria and San Rafael) and multiple early stage targets are hosted within a district scale land package that covers more than half of the historic Peñoles Mining District.
During 2011, Sierra Madre submitted a suite of twenty five, four meter composite core samples, from three widely spaced historic drill holes (CDDH 08-01, CDDH 08-02 and CDDH 08-03) to Inspectorate Exploration and Mining Services of Richmond BC to determine whether or not the mineralization at El Capitan was amenable to heap leaching. According to Inspectorate, 96 hour bottle roll leach tests were completed on each of the composite samples. Gold leach recoveries after 96 hours were estimated at 60%, with recoveries of 70% to 80% on some of the higher grade samples. Gold extraction kinetics for ½” crush size (test C2) indicated that with longer leaching time, gold extraction may improve. Inspectorate recommended that the Company complete additional test work to determine optimal leaching procedures.
Initial systematic column leach testing commenced for El Capitan utilizing approximately 1,200 kilograms of core from the 2011 drill program. While testing is still in progress, Sierra Madre has received a preliminary report documenting initial results from bottle roll tests that were designed to assess the leaching characteristics of three distinct mineralized rock units present at El Capitan. The report discusses interim data; final metallurgical results from Inspectorate have not yet been received nor a report summarizing the mineralogic descriptions, geologic zones, or cross sections. Further data will be useful in putting the initial samples from 2011 drill holes into a broader context.
According to the preliminary report by Inspectorate, grinding to simulate a tank leach scenario significantly improves gold recovery as compared to crushed samples, which is typical for many heap leach evaluations. Even at lower gold grades and with coarse grinds (80% particle size passing (P80) >125 microns) the soluble gold recovery is generally greater than 90%. Depending on the domain and head grade recoveries can approach 99% indicating an excellent response for higher grade ore that is more finely ground.
The preliminary report indicates that crushing (compared to grinding) results in a significant drop in bottle roll recovery despite using longer bottle roll retention times, as would be expected for many gold systems. The volcanic host rocks, which occur in the shallowest areas and are open along strike and down dip, showed the best bottle roll leach response with gold recoveries of 17% to 65%, generally increasing with higher head grades and finer crush sizes. The volcanics are a lumped rock package with varying alteration and mineralization that will need to be evaluated further. There are various rock facies and with only a few initial drill holes this preliminary work only begins to appraise the overall mineralogic character of the Capitan Hill area. The response of deeper sediments is variable and can approach 50% extraction. The material that was classified in the past as the El Capitan Vein, and now is perhaps interpreted as a possible silicified gold-rich horizon near the base of the volcanic sequence, had the lowest response to leaching at the crush sizes so far evaluated, with low soluble gold evident in some testing.
The preliminary column leach testing program at Inspectorate has now been completed. Final assay results from 11 column leach tests representing the three mineralized rock units at various crush sizes (1″, 5/8″ and ½”) and grades will be reported as soon as they are available.
President and CEO of Riverside, John-Mark Staude, stated, “We are pleased to see the Peñoles Project move forward with further testing and results from our partner. Sierra Madre has now completed payments to underlying owners to nearly fulfill the property buyout, with one final payment to be completed in early 2013. Riverside looks forward to unlocking further value at this district scale land package with over a dozen promising precious metal targets.”
In regards to the historic silver mines no additional exploration work has been undertaken in 2012; however, initial trenching and results of a single drill hole completed during 2011 at one of the historic silver mines (Jesus Maria) were encouraging and confirmed that the mineralized zone ranges from 7.5 to 22.0 meters in thickness and is open at depth below the historic mine workings (News Release, November 16, 2011). Previous IP completed by Riverside Resources and geologic mapping and sampling suggest significant strike extent of potentially over 2 kilometers and wide open for the Jesus Maria vein system.
Sierra Madre’s next payment under its option agreement with Riverside is US$250,000, due September 30, 2012, with an additional US$1,650,000 payment due on December 30, 2012. Riverside is pleased with the progress to-date at the Peñoles Project and looks forward to further metallurgical updates and further drilling and exploration progress at El Capitan, Jesus Maria, San Rafael and other high-potential precious metal targets on the property.
The scientific and technical data contained in this news release pertaining to the Peñoles Project were prepared under the supervision of Carl Von Einsiedel, PGeo., a qualified person to Sierra Madre, and reviewed by David S. Smith, MS, MBA, CPG, a non-independent qualified person to Riverside Resources, who is responsible for ensuring that the geologic information provided in this news release is accurate and acts as a “qualified person” under National Instrument 43-101 Standards of Disclosure for Mineral Projects.
About Riverside Resources:
Riverside is a well-funded prospect generation team of focused, proactive gold discoverers with the breadth of knowledge to dig much deeper. The Company currently has approximately $9,000,000 in the treasury and 35,000,000 shares issued. The Company’s model of growth through partnerships and exploration looks to use the prospect generation business approach to own resources, while partners share in de-risking projects on route to discovery. Additional property information about Sugarloaf and other assets that are available for partnership can be found on Riverside Resources Inc. website at www.rivres.com.