Centerra Gold Inc.

Sampling, Analysis, and Data Verification

All Mount Milligan Mine Assay Laboratory procedures are accompanied by appropriate, industry standard instrument calibration and quality assurance/quality control (“QAQC”) measures, including quarterly third-party analysis checks. The ore and acid-base accounting analyses Standard Operating Procedure includes steps to confirm on-site laboratory method accuracy, precision, contamination control, sample tracking, and recordkeeping. The assay laboratory also receives blind duplicate samples from the Ore Control Geologist/Technician which are compared against daily sample analyses. This workflow is managed as part of the Mount Milligan Assay Laboratory Quality Management System.

Most drill core samples analyzed for the Mount Milligan Mine deposits have been collected from NQ-sized core. Cores were either split (early programs) or sawn along the long axis with one-half sampled and assayed and the other half retained in core boxes and the core library. For Centerra operated drill programs, drill core samples (typically NQ width) were cut in half with a diamond saw, with half the sample remaining in the core box as representative, and half the sample sent to an external certified assay lab.

A formal QAQC program, including the insertion of standard, blank and duplicate samples for assay, was introduced after 1992. Prior to that date, external check assays were commissioned from independent laboratories. The QAQC program in place for Centerra drill programs includes regular insertion of CRMs (certified reference materials), coarse blank samples, and both field and coarse reject duplicates. The QC insertion rates are acceptable according to CIM best practice standards, with QC samples accounting for ~15% of the drill hole assay database.

After the assay results were received from the external lab, gold and copper assays were checked by a Centerra database manager using control charts for the CRMs, blanks and duplicates. Any quality control failures (defined as samples bracketing CRMs with assay values ± three standard deviations of the expected value) were documented and relevant batches of samples were requested for re-assay by the lab using the primary pulp. The Centerra database manager completes an annual QAQC report as an internal audit which tracks specific details with any assay lab issues or standard/blank failures.

After completion of the drill programs approximately 5% of the sample pulps from were submitted to a secondary certified laboratory as an independent check for analytical bias and accuracy.

Validation of the mapping co-ordinates, elevations, assay quality control/quality assurance program and the DDH database has been completed by Centerra and predecessor owners of Mount Milligan Mine.

All exploration data is captured as per standard geological data management procedures and is stored in an acQuire Geological Information Management System. Throughout 2025, routine validations and verifications of the database were conducted, including QAQC of all assay data received from external laboratories and verifications of raw data imported into the database, e.g., assay certificates, downhole surveys, geochemical data, and geotechnical data.

The Main Zone includes four contiguous sub-zones: MBX, WBX, DWBX and 66 (low-copper and high-gold grades, southeast of the MBX sub-zone). These geologic zones are the basis for the metallurgical test work.

The Mount Milligan Mine deposit is being mined using conventional open-pit equipment, with the ore being processed through a gyratory crusher, secondary crushing and a SAG-ball mill-pebble crusher combination together with a rougher and cleaner flotation plant, producing a marketable gold-rich copper concentrate.

Metallurgical investigations conducted by various research laboratories prior to commencement of operations conclusively showed that froth flotation is the optimum process for the recovery of copper and gold; with this processing approach being adopted. These investigations were the basis of the performance models used in previous resource modelling. Further investigations and projects have been undertaken to improve the recovery process and update the accuracy of the copper and gold recovery models. Using these new performance models, the LOM average recoveries are estimated at 78.0% for copper and 64.8% for gold.