A resource estimate has been calculated for the Boyongan copper-gold deposit, on the island of Mindanao, southern Philippines.
Philex Gold (PGI-T) and Anglo American Exploration (Philippines) are equal owners of the deposit, located on their 250-sq.-km North project area, in northeastern Mindanao, 20 km north of the provincial capital of Surigao City in the province of Surigao del Norte.
The resource estimate, dated June 10, 2004, was classified according to CIM Standards on Mineral Resources and Reserves.
The resource was divided into two categories, those of oxide and sulphide. An inferred resource of 99 million tonnes grading 0.65% copper and 1.02 grams gold per tonne was estimated in the oxide category and there is 120 million tonnes grading 0.39% copper and 0.51 gram gold per tonne in the sulphide rock.
The estimate was calculated using a 3-D computer block model. A total of 72 holes, totalling 38,421 metres, and drilled to a 100-metre-by-100-metre spacing, was used to calculate the resource.
Copper equivalent cutoff for sulphide material was 0.4%, whereas a cutoff of 0.6% was used for the oxide material. The estimate was based on US$388 per oz. gold and US$1.14 per pound for copper. Recoveries were estimated at 75% for oxide copper, 85% for sulphide copper and 65% for gold.
The deposit is associated with two diorite porphyries buried beneath 50-300 metres of volcaniclastic rocks. Gold mineralization is concentrated closer to the intrusions, especially in areas of quartz stockwork adjacent to the intrusives. There is a shallow, oxide, copper-gold zone, that is primarily composed of cuprite, azurite, malachite, chrysocolla, neotocite, chalcocite and native copper. This is followed by a transitional oxide-sulphide zone, and at greater depth a sulphide zone containing pyrite, chalcopyrite, bornite and rare molybdenite.
Philex Gold and Anglo American Exploration (Philippines), a wholly-owned subsidiary of Anglo American (AAUK-N) operate the project under jointly-owned Silangan Mindanao Mining. The resource calculation was verified by consulting firm AMEC Americas.
Exploration continues in other areas of the North project. The Bayugo zone, 1,200 metres northwest of Boyongan, was drilled in 2003. Highlights from two drill holes were recently reported; one intercept graded 0.43% copper and 1.08 grams gold per tonne over 58 metres, while a separate hole intersected 39 metres grading 1.28% copper and 0.83 gram gold per tonne.
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