Wheaton Precious Metals Corp.

Sampling, Analysis and Data Verification

Exploration

Sample preparation details prior to 2002 are unknown. During 2002 – 2003, sample preparation was conducted by Lakefield / GEOSOL laboratory at a local facility built at the Salobo mine site.

During the 1978 campaign, samples were assayed at the Docegeo laboratory in Belém, Pará, and at the SUTEC laboratory in Santa Luzia, Minas Gerais. Copper was assayed on 0.5 g aliquots by multi-acid digestion and atomic absorption spectroscopy (AAS). Iron, molybdenum, and silver were also determined using this method. Gold was assayed by aqua regia leaching, with solvent extraction (MIBX) and AAS determination.

During the 1986 campaign, CVRD assayed the samples at the Docegeo laboratory in Belém and at the pilot plant laboratory on the mine site, using the same analytical methods as in the previous campaign.

During the 1993 campaign, SML used the Mineração Morro Velho (MMV) laboratory. Copper was again assayed with multi-acid digestion and AAS reading on 0.5 g aliquots (0.002% detection limit), and gold was determined using the fire-assay method with gravimetric finish on 100 g aliquots (0.05 g/t detection limit). In addition, samples were assayed for sulphur and carbon by LECO, and fluorine by alkaline fusion with sodium carbonate and potassium nitrate, followed byion-selective electrode determination. SMSA used the same analytical procedures during the 1997 campaign.

In the early stages of the exploration program platinum, palladium, nickel, molybdenum and uranium were also analyzed; however, these elements were later excluded from the analytical package.

The infill and deep drilling programs that began in 2010 are using sample preparation procedures similar to the 2002 – 2003 campaign. Sample preparation was being done at the Salobo mine laboratory but was switched to ALS, Vespasiano, Minas Gerais, Brazil in December 2018 in order to advance the backlog of pending samples. In September 2021 the sample preparation was moved to ALS, Parauapebas, Para, Brazil. Since 2017, samples are being analyzed at ALS, Lima, Peru as the primary lab and since March 2018 SGS Geosol, Belo Horizonte, Minas Gerais, Brazil has been used as the check assay laboratory.

Grade Control

Blast-hole samples are prepared and assayed at the Salobo mine operations laboratory which has separate areas for the preparation of concentrate, tailings and blast-hole samples to avoid contamination. The preparation laboratory is well organized, and has modern equipment including ESSA jaw crushers, rotary splitters, puck-and-bowl pulverizers and Mettler-Toledo precision scales. A special, separated, scale room is used only for gold assays. The dust-extraction system is in place to reduce the chances of sample contamination.

Blast-hole samples are assayed at the Salobo mine operations analytical laboratory for copper, gold, silver iron, carbon, sulphur, fluorine, chlorine and soluble copper.

Assay batches are usually organized in 25 samples, not including the internal control samples. The lab’s quality control (QC) protocol includes the insertion of one reference material, one reactive blank (consisting of pure solution or flux in the case of FA), one coarse duplicate, and one pulp duplicate per batch.

Quality Assurance and Quality Control

QA/QC programs before 2002 mostly included seldom submission of external assay checks and, to lesser extent, standard reference material (standard) samples and coarse duplicates.

Are-assay program was undertaken in 2002–2003 to validate the pre–2002 data, and following that program, the earlier data that were notre-assayed for lack of analytical material were accepted for use in estimation.