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recent key projects

Pinto Valley mine

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.

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MantoVerde Mine
HEAP LEACH Optimization &
Cobalt Recovery


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.

Aktogay Mine

KAZ Minerals, 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.

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Gold Springs Resources, UTAH/NEVADA

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.

bonnie claire

iconic minerals, NV

In 2021, GRE created an NI 43-101 Preliminary Economic Assessment (PEA) for the Bonnie Claire lithium project in Nevada.  GRE is currently involved in advancing this work into a Pre-Feasiblity Study.  This project involved the following elements: Calculation of a mineral resource estimate; Creation of a mine plan for lithium-rich clay extraction; Design of a metallurgical testing program and a metallurgical plant, and Creation of an economic model
To access deeper high-grade lithium, GRE evaluated the use of innovative borehole mining methods which will allow for the exploitation of the high-grade lithium clays below lower-grade cover.  


GRE’s team is working with Bonnie Claire and a respected metallurgical lab to design the process flowsheet for producing battery-grade lithium carbonate.   The first sample of battery-grade lithium carbonate has been produced.  GRE will be the lead author on the upcoming Pre-Feasibility Study.   

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punitaqui project

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.

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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.


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. 


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.



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.


corani project

bear creek mining corp, peru

GRE has been involved with the +300 million ounce silver, lead, zinc bulk tonnage open pit project since 2011. The project is located at an elevation of 5,000 meters in challenging terrain. GRE’s initial responsibilities included geotechnical, hydrogeologic, and environmental drilling and site investigation programs for the project Feasibility Study (FS) and Environmental Social Impact Assessment (ESIA) permitting (in Spanish) in 2012. In 2014-2015, GRE completed a project optimization study of mine, process, tailings, and hydrologic aspects of the project, followed by a FS update that included the resource estimate, mine plan, and geometallurgical model, with input on process design. The geometallurgical model utilized state of the art non-parametric statistical methods to create a multivariate adaptive regression model that greatly improved the spatial understanding of metallurgical response, allowing GRE to optimize the mine plan, significantly enhancing project economics. In 2017, GRE provided Qualified Persons oversight of the Phase 1 Front End Engineering Design Study involving geology, resource, reserve, hydrology, geochemistry, mining, marketing, and project economic models.

clayton valley

century lithium, nv

Century Lithium owns 100% of the Clayton Valley Lithium Project  totalling 5,585 acres in west central Nevada, USA. Exploration and development by Century led to the discovery of an extensive resource of lithium-bearing claystone, immediately adjacent to the lithium brine basin in the valley. The lithium resource is exposed at surface, sheltered from erosion by Angel Island, an outcrop of Cambrian metavolcanic and clastic rocks, protruding through the Pliocene lakebed sediments.


At present, the Company is actively processing material from its lithium-bearing claystone deposit at its lithium extraction facility in Amargosa Valley, Nevada. While moving toward the completion of a Feasibility Study and subsequent permitting, with the goal to become a domestic producer of lithium for the growing electric vehicle and battery storage market.

GRE was first contracted to develop a Preliminary Economic Analysis 43-101 technical report and is now a key member of the FS team working on the resource and mine plan.


aurizona mine

prefeasibility study

equinox 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.




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.



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.

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