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 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.

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.

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 2024, 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.

Mount Milligan Mine is a copper-gold porphyry deposit, consisting of two principal zones, the Main Zone and the Southern Star (SS) Zone. 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 78.9% for copper and 65.9% for gold.