Highlights included 50m at 0.56% copper, 0.5g/t gold and 236.4g/t silver; and 36m at 1.45% copper.

"We expect to convert a large portion of our inferred oxide resource to indicated, which was one of our primary objectives this season," CEO Adam Lundin said.

Filo released a preliminary economic assessment on the oxide portion of the project's existing resource in November, which outlined an after-tax NPV (8% discount) of US$705 million and a 3.6-year payback using a $3 per pound copper price.

It put initial capex at $792 million for a 13-year mine producing an average annual 50,000 tonnes of copper, 115,000 ounces of gold and 5.13 million ounces of silver.

The company is well-funded as it works on a prefeasibility study, having closed a C$25.5 million (US$19.9 million) share offering and private placement in February.

Metallurgical testwork began earlier this month and the company said it was laying the groundwork for future environmental assessments and project permitting.

Filo shares last traded at C$2.50, valuing it around $180 million.