Name of the Mine 
Didipio mine.

Location 
The Didipio operation is in the northern Luzon region of the Philippines and straddles a provincial boundary, with parts of the property in Nueva Vizcaya and Quirino provinces.

Mine Owner/s 
OceanaGold Corporation, through its wholly-owned subsidiary, OceanaGold (Philippines).

Brief Description 
Didipio is an operating gold/copper mine that has transitioned from openpit to underground mining. The mine has a significant life-of-mine remaining and is a key asset for OceanaGold in the Philippines.

Brief History 
Alluvial gold was first discovered in the Didipio area in the 1970s by local miners. 

Various companies conducted exploration activities from 1975 onwards. In 1994, the Financial or Technical Assistance Agreement (FTAA) was executed, granting rights for large-scale exploration, development, and mining. OceanaGold acquired control in 2006. 

Construction started in June 2011, with openpit mining starting in July 2012 and commercial production declared in April 2013. The openpit was completed in April 2017. Underground development started in April 2015, and first stoping occurred in December 2017. Operations were suspended in July 2019 following the expiry of the initial FTAA term but resumed in November 2021 after the FTAA was renewed for another 25 years.

Primary Metals/Minerals 
Gold and copper.

Secondary Metals/Minerals  
Silver.

Geology/Mineralisation 
The Didipio gold/copper deposit is hosted within the multiphase Didipio Stock, part of a larger alkalic intrusive body known as the Didipio Igneous Complex. It is identified as an alkalic gold/copper porphyry system, roughly elliptical at the surface (480 m long by 180 m wide) with a vertical pipe-like geometry extending to at least 800 m below the surface.

The local geology consists of north-northwest-trending, steeply east-dipping composite monzodiorite intrusive, in contact with volcaniclastics of the Mamparang Formation. Porphyry-style mineralisation is closely associated with K-feldspar alteration within a porphyritic monzonite stock.

The main economic minerals are chalcopyrite, gold, and silver (electrum). Chalcopyrite occurs as fine-grained disseminations, aggregates, fracture fillings, and veins. Fine-grained gold occurs as micro-inclusions in sulphides, as well as free gold, electrum, and telluride. Oxidation of sulphides extends from the surface to a depth of 15 m to 60 m (averaging 30 m).

Reserves 
As at December 31, 2024, the mine had total proven and probable mineral reserves of 45.7-million tonnes grading 0.84 g/t gold.

Resources 
As at December 31, 2024, the mine had total measured and indicated resources estimated at 49-million tonnes grading 0.92 g/t gold and inferred resources of 6.4-million tonnes grading 0.8 g/t gold.

Type of Mine 
Underground mining, supplemented by processing of surface stockpiles from previous openpit operations.

Mining Method 
The primary underground mining method employed at Didipio is longhole open stoping with paste backfill. The mining sequence has been altered to a top-down method (as opposed to bottom-up) to access high-grade ore earlier and reduce geotechnical risk. 

Stope dimensions vary based on ground conditions, with dual lift stopes (up to 60 m high) in the Monzonite zone and more conservative dimensions in the Breccia zone owing to poorer ground conditions. 

Major Infrastructure/Equipment 
The mine comprises a 4.3-million-tonne-a-year processing plant producing gold doré and copper concentrate, using froth flotation following a conventional semiautogenous grinding mill/ball mill pebble crushing grinding circuit and gravity gold recovery circuit.

Underground infrastructure includes an access decline, ventilation raises (exhaust and fresh air), underground ladderway system for egress, permanent refuge chambers, underground lunchroom, substations, dewatering stations, sumps, service holes for paste backfill and electrical cables, and a surface workshop.

Infrastructure further includes a tailings storage facility, a power supply connected to the national grid through a 69 kV dedicated line, with a diesel-powered backup power station on-site; a water treatment plant; a site-based sewage treatment plant, and various water storage ponds.

A road provides access to port facilities at Manila (for inwards transit) and Poro Point, La Union (for concentrate departure).

A site-based camp offers single-status accommodation for personnel.

Prospects 
A prefeasibility study (PFS) is in progress. The PFS will focus on identifying uplift requirements to support an optimised underground mining production rate of about 2.5-million tonnes a year. The PFS will also identify the preferred process plant operational throughput rate for the optimised underground operation and evaluate process plant augmentation requirements to scale to, and sustain, the already permitted 4.3-million-tonne-a-year processing rate. The PFS will be released after the completion of resource conversion drilling, and the completion of other ongoing dewatering work, and is now expected to be completed in 2026.

Contact Details 
OceanaGold Corporation
Tel +63 78 362 1026
Email DidipioMine.IR@oceanagold.com
Website  https://didipiomine.com.ph/ or https://oceanagold.com/