The Boa Esperanca copper project is an open-pit copper mine planned to be developed by Ero Copper in Para, Brazil. Ero Copper is a base metals mining company based in Vancouver, British Columbia, Canada.
The company acquired 85% interest in the project from Mineracao Caraíba (MCSA) in December 2016. It further acquired 14.5% stake in the project in June 2017.
The Boa Esperanca copper property was initially held by Chilean state-owned copper mining company Corporacion Nacional Del Cobre (Codelco). MCSA had acquired the project from Codelco in 2007.
While Ero Copper completed a feasibility study (FS) of the project in June 2017, it announced the results of an optimised feasibility study in September 2021.
The construction works are expected to be started in the second half of 2022 and the mine is expected to produce 326,000 tonnes (t) of copper over an initial mine life of 12 years. The initial capital investment on the project is estimated to be £215m ($294m).
Copper production from the Boa Esperanca mine
The average annual copper production from the Boa Esperanca mine in the first five years of operation is expected to be 35,000t at a mill throughput processing rate of four million tonnes of ore per annum (Mtpa).
The average annual copper production during the initial 12 years of mine life is estimated to be 27,000t.
Location, geology and mineralisation
The Boa Esperanca copper project is located approximately 40km south-west of Tucuma in the Brazilian state Para.
The project is situated within the Carajas Mineral Province, on the east side of the Amazon Craton. Carajas is one of the most prolific mineral provinces in Brazil. It hosts high-grade iron deposits as well as world-class copper-gold deposits including Salobo, Sossego, Cristalino, Igarape Bahia, and Alemao.
The Boa Esperanca copper deposit lies within an isolated hill with mineralisation hosted in a series of brecciated zones comprising quartz, magnetite, and the Neoarchean biotite granite.
Copper reserves at Boa Esperanca
The Boa Esperanca copper project was estimated to hold 43 million tonnes (Mt) of proven and probable ore reserves grading 0.83% copper as of August 2021. It included 30.7Mt of proven and 12.4Mt of probable reserves containing a total of 356,600t of copper.
The measured and indicated resources of the project are 47.7Mt grading 0.86% copper.
Mining and processing
Conventional open-pit mining method using 4m3 hydraulic excavators and 35t trucks will be employed to extract and haul ore to the primary crusher or the run-of-the-mine (ROM) stockpiles. Waste rocks will be hauled to dump sites.
The ROM ore will undergo three-stage crushing followed by screening, jigging, and ball mill grinding. Further, it will pass through rougher and cleaner flotation to produce copper concentrate, which will be thickened, dewatered, and filtered before shipping.
The other infrastructure facilities will include a tailings storage facility, waste rock dumps, workshops, and storage areas for fuel and explosives.
The project is estimated to require up to 9.1MW of electricity, which will be supplied through a 138kV power transmission line from the regional grid.
Contractors involved in the Brazilian copper project
SRK Consulting, a mining consultancy firm based in Canada, was contracted by Ero Copper to prepare the feasibility study of the Boa Esperanca copper project in 2017. SRK was also previously engaged by MCSA to prepare an initial feasibility study of the project during 2011 and 2012.
DrillGeo Geologia e Sondagem, a company based in Brazil, has been engaged as the third-party drilling contractor for the project.