Asset Overview

Josemaría is a copper-gold (Cu-Au) porphyry system located in the Andes Mountains of San Juan Province, Argentina. The project is located about 10 km from the Chilean border and is about 140 km southeast of the city of Copiapó, Chile and 350 km northwest of the city of San Juan, Argentina.

Project NameJosemaria
LocationArgentina (Andes near border)
Elevation4,300 m
StatusPFS Complete

On November 20, 2018, the Company announced positive PFS results on its 100% owned Josemaria Project. (see press release dated Nov 20, 2018).

On December 19, 2019 the Company subsequently filed a Technical Report on the Josemaría Project entitled "NI 43-101 Technical Report, Prefeasibility Study for the Josemaría Copper-Gold Project, San Juan Province, Argentina" (the "Josemaría PFS"). Subsequent to the disclosure provided in the Company's news release dated November 20, 2018, a non-material change was made to the capital and operating cost estimates, resulting in minor adjustments to the initial capital cost, sustaining capital cost, capital cost spend profile over the life of mine, and operating costs. These changes and their impact on economics are reflected in the information provided below (see press release dated Dec 19, 2018).

Josemaría PFS Executive Summary

The PFS contemplates that Josemaría would be mined using conventional open pit methods and assumes the latest in autonomous haul truck technologies. From the open pit, ore would be trucked to a primary crusher, crushed, and then sent to the process plant.  The comminution circuit design considers a high-pressure grind roll (“HPGR”) crushing circuit followed by ball mill grinding.  The circuit was designed to process 150,000 tonnes per day of ore. Conventional sulphide flotation will follow the comminution stage and is expected to produce a gold and silver-rich copper concentrate.  Groundwater for the process plant would be supplied from nearby aquifers to the plant site, and power would be supplied via 250 km of power line construction to connect to the Argentine national grid.  Concentrates would be trucked from the plant to the port of Caldera in Chile, approximately 380 km by road from the Josemaría plant site, requiring the construction of 57 km of new road to connect to the public highway.

Josemaria PFS Highlights:

  • A $2.0 billion after-tax NPV using an 8% discount rate and an IRR of 18.7% at $3.00/lb copper;
  • Strong front end production and cash flows drive a 3.4 year payback period and support a variety of financing alternatives;
  • An Initial Probable Mineral Reserve of 1,008 Mt of 0.29% copper, 0.21 gpt gold, and 0.92 gpt silver (or 0.41% CuEq);
  • Pre-production capital cost of $2,761 million (excluding costs prior to a construction decision);
  • Average annual production (rounded) of approximately 125,000 tonnes of copper, 230,000 ounces of gold, and 790,000 ounces of silver per year at a C1 cost of $1.26/lb CuEq;
  • First 3 years full years of annual production average 170,000 tonnes of copper, 350,000 ounces of gold, and 1,000,000 ounces of silver;
  • 20 year mine life producing over 5.4 billion lbs of copper and 4.6 million ounces of gold;
  • Low strip ratio of 0.71:1 (waste:ore);
  • Excellent metallurgy producing a clean, marketable, precious metals rich copper concentrate;
  • Design incorporates planning for a fully autonomous haul truck fleet along with high pressure grinding rolls;
  • All major mining and infrastructure located in San Juan Province, Argentina – facilitating permitting in one jurisdiction;
  • Potential opportunities to further improve the project include:
    • Recovery of additional gold from the oxide cap at Josemaría;
    • Increasing metallurgical recoveries and concentrate grades with additional test work and optimization; and
    • Delineating more or higher-grade material through continued exploration on the Company’s extensive land package.

Summary of Josemaría PFS Economic Results:

Pre-Tax NPV (8%) & IRR$2.9 billion NPV
21.4% IRR
After-Tax NPV (8%) & IRR$2.0 billion NPV
18.7% IRR
Undiscounted After-Tax Cash Flow (LOM)$6.6 billion
Payback Period from start of processing
(undiscounted, after-tax cash flow)
3.4 Years
Metals Prices Assumed$3.00/lb Cu
$1,300/oz Au
$20.00/oz Ag
Initial Capital Expenditures (rounded)$2,761 million
LOM Sustaining Capital Expenditure (excluding closure)$860 million
LOM C-1 Cash Costs (Co-Product)$1.26/lb CuEq
Nominal Process Capacity150,000 t/d
Mine Life20 years
Average Annual Metal Production (rounded)First 3 years
(full production)
Life of Mine
170,000 t Cu
350,000 oz Au
1,000,000 oz Ag
125,000 t Cu
230,000 oz Au
790,000 oz Ag
LOM Average Process Recovery86% Cu
71% Au
59% Ag

Josemaria Property Summary


NGEx owns a 100% interest in the Josemaria deposit.


The Josemaría deposit is located in the Andes Mountains of  San Juan Province, The project is located about 10km from the Chilean border and the shortest access to the Project is from Copiapó Chile, a driving distance of about 170 km, or three hours.  Access from Argentina is by major provincial highways and dirt roads from the city of San Juan, Argentina.  Copiapó has a population of approximately 150,000 people, an airport with daily scheduled flights to Santiago and Antofagasta, and companies that offer mining and exploration services.  While farther away, San Juan, Argentina, is also a major mining centre with good mining services available.

The climate in the Project area is dry to arid and the temperatures are moderate to cold.  Annual precipitation is about 250 mm, with snow at higher altitudes in the winter.  Exploration fieldwork is generally carried out from mid-October to early May.  It is anticipated that mining operations will be conducted year-round.

The Los Helados Deposit also held by NGEx is located 10 km to the northwest in Chile.


Josemaria is a grass roots discovery made by NGEx and there is no record of significant exploration activity prior to NGEx’s interest.


Josemaría is a copper-gold (Cu-Au) porphyry system. 

The copper-gold mineralization at Josemaría is mostly hosted by a Miocene porphyry system which forms an elongated body with minimum dimensions of 800 to 900 m north-south, 600 to 700 m east-west and 600 to 700 m vertically. The porphyry has been dated at approximately 24.7 Ma. The main hypogene Cu and Au mineralization is associated with the upper parts of the potassic alteration zone. Chalcopyrite and pyrite plus minor bornite are disseminated through the potassic zone. Quartz–magnetite ± chalcopyrite veining occurs through much of the main mineralized zone, as discrete veins and locally as a more intense stockwork.

A well-developed leached cap overlies the entire Josemaría deposit, related to oxidation at and below the present topographical surface. There have been at least two main stages of supergene copper enrichment at Josemaría: the first occurring prior to the deposition of the post-mineral volcanic rocks and a second phase occurring at the present-day erosional surface. Along the Josemaría structural corridor, a distinct inverted bell-shaped concentration of secondary copper mineralization forms the richest part of the enrichment blanket.

The Josemaría deposit remains open to the south, beneath a thickening cover of post-mineral volcanic rocks, and also at depth.


Work programs conducted by NGEx include geological mapping; soil, rock-chip, and talus sampling; a number of geophysical surveys including induced polarization (IP)–resistivity, magnetometer, and Mount Isa Mine’s Distributed Acquisition System methodology (MIMDAS) surveys; reverse circulation (RC) and core drilling, and Mineral Resource estimation.  A number of environmental baseline studies have been undertaken. 


Nine drilling campaigns have been carried out at the Josemaría deposit, from 2003 to 2014.  Drilling at the Josemaría deposit to date totals 61,100 m in 142 drill holes, of which 48 holes (17,535 m) are RC holes, and 94 holes (43,565 m) are core holes.  Core recovery from holes drilled at Josemaría between 2011 and 2014 averages 94%. 

Resource Estimate

Link to Resource Estimate

Metallurgical Testwork

A two-phase metallurgical test work program for Josemaría was conducted at SGS Minerals S.A. laboratories in Santiago, Chile. SGS Minerals S.A. laboratories is independent of the Company.  Multiple composite and variability samples were tested for mineralogy, physical characterization, gravity concentration, conventional sulphide flotation (open/locked cycle tests with different flowsheets), flotation tailings cyanidation and solids settling.  Based on the testwork completed to date, life of mine metal recovery is expected to be 86% for copper, 71% for gold, and 59% for silver.   Copper concentrate grades are expected to average 25% over the life of the mine.   It is anticipated that the concentrate will be clean, precious metals rich, and readily marketable.

Recent metallurgical testing performed at ALS, Kamloops, BC focused on confirming and improving the bulk concentrate flotation results achieved by SGS.  ALS is also independent of the Company.  The work generally confirmed the results and identified several areas that could be explored to increase the overall copper concentrate grades while maintaining similar recoveries.   Additional test work is planned during the 2018 / 2019 field season to optimize this work as Josemaría transitions into a Feasibility Study.

Mining and Processing

The study contemplates conventional open pit mining methods using autonomous haul trucks.  Mine planning incorporates stockpiling strategies to focus on the early extraction of the highest-grade ore in addition to deferring waste stripping.  Including pre-stripping, the open pit will be in operation for 23 years, delivering ore to the mill for 20 years, with a life of mine strip ratio of 0.71:1.   A maximum mining rate of approximately 115 Mt per year (including waste) is required to provide the nominal 150,000 tonnes per day of ore to the mill.  A total of 1,008 Mt of ore is expected to be processed over the life of the mine.

Primary crushed ore will be transported via surface conveyor to a coarse ore stockpile, and then transferred to the process plant.   The process considers the use of HPGR’s as part of a three-stage crushing circuit, followed by conventional ball mill grinding and sulphide flotation.  Design throughput is 150,000 tonnes per day.  Water obtained from the concentrate thickener, tailings thickener and concentrate filter will be recovered and sent back to the process plant to be used as make-up water.

The proposed PFS production schedule and metal production profile is shown on the attached figures.  Note: the project assumes a 30-month construction period, which would begin mid-way through Year 1.

Figure 1 – Josemaria PFS Production Schedule

Figure 2 – Josemaria PFS Metal Production Schedule

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