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gold | copper | silver

pinto valley

capstone copper, az

GRE has been involved with the Pinto Valley porphyry copper project since 2018 (Capstone Copper). Initial work involved analysis of the concentrator performance and recommendations for performance improvements. GRE was the QP for the first PV3 43-101 update report. The project scope evolved to include operator flotation training, mass balance reconciliation, and sampling program, geotechnical analysis of the heap leach, heap leach optimization, pumping systems review, site water balance, MetSim modeling (Mill and HLF).  

Most recently GRE has been tasked with examining the heap leach performance in both a column test program and a large demonstration heap (designed and operated by GRE).  The goal is to better understand the performance of the Jetti technology. 

GRE is also working with PV on their site-wide water balance developing a Goldsim model and assisting with securing adequate water for future operations.


GRE continues to support the upcoming PV4 43-101 technical report.

aktogay mine

kaz mineral, kazahkstan

The Aktogay mine has two existing oxide heap leach pads.  The ore is primarily oxide but has significant sulfide copper present reducing acid-based copper extraction.  The current heap, DLP2, is ~100.000 tpd. 


GRE was tasked with the conversion of an existing copper oxide heap leach to a bioleach. The project commenced with column test work and bacterial adaptation to a mature raffinate. Test work indicated that a significant copper extraction increase was possible. 

GRE designed an inoculation system to deliver mesophile bacteria to the heap leach as well as an aeration system (including controls) to provide oxygen for bioleaching,   


Test work is currently underway examining the use of this system for a large resource of low-grade primary sulfide ore.

gold springs

gold springs resources, utha/NV

GRE provided structural geologic mapping support, metallurgical test work support, completed several mineral resource estimates, and PEA of the nearly million ounce Gold Springs heap leach gold/ silver project.


The work consisted of numerous pit sizes and production rates identifying various viable scenarios. The results were further analyzed to determine the most robust economic scenario to advance to the next level of study. GRE is continuing its involvement in the project as it advances to the PFS stage.


world copper, chile

The Escalones copper porphyry project lies 35 km east of El Teniente, one of the world’s largest underground copper mines, and within the renowned Chilean porphyry copper belt that runs north-south in the central Andes Mountains. The project has excellent infrastructure, including road access, electricity, access to seaports, and a gas pipeline that crosses the 70 square km property.


The Escalones deposit was discovered in 1996 through greenfield exploration. In 2020, World Copper recognized that the shallow, higher-grade mineralization is significantly oxidized, rendering it mostly acid-soluble and potentially amenable to cost-effective, heap-leach copper production.  GRE was responsible for developing a Preliminary Economic Analysis 43-101 technical report on the project.

Redefining the project as a copper oxide deposit significantly enhances its value by lowering costs of capital and operating development options compared to the previously contemplated sulfide flotation project.


capstone copper, chile

GRE working with Capstone and site personnel developed an optimization strategy for the existing dynamic and dump leach systems.  The goal of the project is to reduce costs and increase copper production.

GRE has also been engaged in a cobalt recovery project that involves the addition of cobaltiferrous pyrite to the dynamic leach system.  The pyrite is sourced from the cleaner scavenger flotation tailings.  The addition of a heap aeration system and an inoculum system is currently under design.

GRE has assisted in the development of a test program for the leach system along with a cobalt recovery pilot plant.

florida canyon

argonaut gold, nv

Florida Canyon is an open pit and heap leach gold recovery mining operation that has been operating since 1986. Florida Canyon is located approximately 45 miles southwest of Winnemucca, Nevada. An updated mineral resource was prepared by SRK Consultants (US) in November 2018.


GRE was contracted to review the heap leach operation and groundwater impacts as well as develop a geometallurgical program aimed at examining the large underlying sulfide resource.


battery minerals, chile

GRE was contracted to assist in bringing the Punitaqui project back online.  The project consists of a mine complex including four underground mines and a 4,000 tpd copper sulfide flotation concentrator. The site was previously operated by Glencore.

GRE was initially involved with the supervision of process test work including variability testing.  This data was used to develop a modified plant flowsheet using MetSim.  GRE has also been actively involved in the evaluation of a novel filtration system for plant tailings.

The project has evolved to include a review of the resource, mining methods, and costs as well as developing a plan of operations for the restart.  GRE will be involved in the commissioning and start-up of the plant later in 2023.

eskay creek

skeena resources, bc

Eskay Creek is a precious metal-rich volcanogenic massive sulfide (VMS) deposit. The mineralization at Eskay has been the focus of considerable exploration activity dating back to 1932. During exploration in 1988, the 21A and 21B zone were first discovered which eventually led to the opening of the Eskay Creek Mine in 1994.

Eskay was the highest-grade gold mine in the world when in production. The mine produced 3.3 million ounces of gold and 160 million ounces of silver at average grades of 45 g/t gold and 2,224 g/t silver from 1994 -2008.

GRE is involved in updating the recent feasibility study including mine planning and gold recovery. 

Corani Project

Bear Creek Mining Corp., Peru

GRE has been involved in the Corani Project since 2011 initially completing the mine water characterization, pit dewatering, and tailings facility design for the first feasibility study.  Since that time, our scope has grown to include the resource estimate, mining, metallurgy, and geometallurgical model for several updates to the feasibility study and an optimization study. In 2011, managed a feasibility level field program and assisted with the preliminary design for the mine tailings storage facility, waste rock dumps, and mine pit dewatering program.  Field program included oriented core drilling, packer testing, aquifer testing, test pitting, and standard penetration tests.  In 2012, assisted with the bankable feasibility study level design for the tailings storage facility, waste rock dumps, water storage, and ancillary facilities.  Project manager for in-country technical personnel.  Also assisted extensively in the preparation of the environmental and social impact study.  In 2013, assisted extensively in the preparation of the environmental and social impact study by writing original technical documents to substantiate the mine development and mitigation programs.  Also completed the bulk of the Spanish translation of those documents.  The final ESIA was approved by the Peruvian government in Nov 2013.  In 2014, created a multi-scenario deterministic economic model to complete a whole project optimization stud.  The model evaluated trade-offs for the tailings disposal, plant primary crushing system, waste dump locations, mining sequence, cut off grade, mining equipment fleet, varying pit limits, and process plant locations resulting in an initial CAPEX savings of $66M and an increase in NPV5 of $47M.  In 2015, assisted with the updated feasibility study, this time responsible for the resource calculation, mine design, mine scheduling, co-disposal tailings and waste rock design, and geometallurgical model.  In 2016 and 2017, assisted in country engineering groups with the Front End Engineering Design (FEED).

aurizona mine

equixon gold, brazil

For the Pre-Feasibility Study (PFS), GRE performed the following: waste rock storage facility design, pit dewatering predictions, surface water management plan, geochemical characterization, pit slope stability, and acid rock drainage (ARD) management plan. Key challenges to the project included the remote location, the management of saprolitic soils, the management of extreme seasonal precipitation, and the close proximity of the Atlantic Ocean to the pit (which ultimately will be significantly below sea level). The GRE team performed multiple rounds of hydrogeologic, geotechnical, and geochemical field characterization. The team created an integrated slope-stability model and hydrogeologic model for the pit that allowed for an optimized pit slope angle (thus saving waste rock production). In addition, GRE saved significant capital by optimizing the existing water management infrastructure from the prior mine operation. The end result of the effort was a PFS with a positive economic outcome that permitted rapid financing.

castle mountain

equixon gold, brazil

GRE was been retained by Newcastle Gold to perform the open pit mine optimization, mine design, and capital and operating cost estimates for the previously producing, 4.0 million ounce Castle Mountain gold project in Southern California. Key features of the project include land and water constraints that required innovative solutions. The study is expected to be finalized in the first half of 2018.


barrick gold, ontario

Hemlo has produced more than 21 million ounces of gold and has been operating continuously for more than 30 years. Located just north of Lake Superior on the Trans-Canada Highway, about 35 kilometers east of Marathon, Ontario, it’s currently an underground operation.

GRE was contracted to conduct a mill audit related to improving the reconciliation of the gold produced.  GRE conducted a statistical analysis of the gold assays and samples using the Guy equation to determine the relative errors present in the mass balance.

inde mine

eci exploration, mexico

GRE has been involved with the multiple narrow vein Inde Mine since 2013 including resource updates, plant refurbishment, tailings facility construction design, plant restart operational audit, mine closure liabilities assessment, mining operations support, and historic tailings deposit resource assessment.  


The initial tailing facility construction design involved the adaptation of a partially constructed facility to meet current industry standards.  This involved modifying the constructed decant system to safely discharge recycled water to the process plant and fully lining the facility.   The plant audit included oversight of a comprehensive plant stream sampling program to identify different ore types and maximize the recovery of gold and silver.  The mining operations support consisted of mine planning training and forensic account analysis to develop an 18-month operating budget using site-specific productivity, unit costs, and consumption rates.  


The operating budget was used to develop a new accounting system to better track capital and operating costs expenditures.  A significant success story of the operation is the conversion of the historic tailings facility into a mining resource.  The conversion of the facility from an environmental liability into plant feed resulted in a 2-year positive cash flow for operations.  GRE’s continued involvement consists of a new tailings dam construction design including the preparation of documents for permitting including technical translation to Spanish.

marlin gold project

montana Exploradora (Goldcorp), Guatemala

Provided onsite design support and contract management during the construction of the tailings facility, associated crushing facility, and steel works; and managed the survey and laboratory QA/QC personnel.  Reviewed and approved contractor payment requests, completed numerous change orders and concurrent justifications, assisted in the preparation of the as-built drawings, prepared up to date expenditure and variance reports, directed the contractor in the field through work directives, reviewed the completed work to ensure adherence to design specifications, reviewed numerous lab reports verifying the quality of construction materials, and completed a quarry design for the rock borrow.  For the subsequent phases of construction, completed detailed construction sequences, calculated placement quantities and prepared cost estimations based on those quantities.  Completed the construction of both phases in the time allowed overcoming numerous material shortages and production challenges.  The contracts for both phases were closed $US 1.2M under final budget.

escobal project

tahoe resources, guatemala

GRE completed a groundwater characterization study, including the installation of a monitoring well network, packer tests of boreholes, and multiple-well aquifer tests. GRE created groundwater models to assess the effects of underground mine dewatering on local and regional water sources. The results of the study were included in the ESIA for the Escobal Project.

santa elena mine

silver crest mines, mexico

Conducted several environmental audits of the operating facility.  Performed key studies in support of mine development and mine permitting including a water supply study that discovered a clean, abundant water supply close to the mine. This discovery saved the project the necessity of installing a 13-kilometer water line. Conducted a geochemical study that quantified and mitigated acid-rock drainage (ARD) risk. Created a comprehensive Environmental Management Plan and taught on-site personnel how to perform routine environmental monitoring. Assisted with the groundwater model design for the pit dewatering requirement.  Also completed the technical translation of the final report from English to Spanish.

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