Shares in Greatland Resources Ltd (AIM:GGP, OTC:GRLGF, FRA:G8G, ASX:GGP), the gold and copper miner, are up a further 13% to 665.2 in London trading on Wednesday as investors continued to digest landmark resource update at its Telfer operation in Western Australia.

The gains have been amplified by a broader re-rating of precious metals stocks, with gold rising 1.8% as conciliatory rhetoric from Iran eases tensions in the Middle East.

The stock advanced strongly on Monday when the company announced a 150% expansion in the mineral resource at Telfer, taking the total to 8 million ounces of gold and is up more than a quarter in value since the start of the week.

The updated December 2025 estimate adds 4.8 million ounces of gold at a discovery cost of approximately $5 per ounce.

The higher-confidence measured and indicated category, which provides a stronger foundation for mine planning and conversion into mineable reserves, grew 163% to 3.8 million ounces.

Combined with the adjacent Havieron deposit, Greatland's total gold and copper resource now stands at 14.9 million ounces of gold equivalent and 645,000 tonnes of copper.

The resource spans open pit, underground and stockpile sources, with the West Dome Open Pit contributing 4.9 million ounces, the Main Dome Underground 2.2 million ounces, and a maiden West Dome Underground resource of 0.6 million ounces at grades of approximately 2.3 grams per tonne.

The growing contribution from higher-grade underground zones is expected to play an increasingly important role in future production planning, with the West Dome Underground considered geologically similar to the existing Main Dome Underground operation and remaining open for further extension.

The expanded resource base supports the long-term viability of Telfer's existing processing plant, which handles 20 million tonnes of ore per annum and which Greatland took ownership of in December 2024.

Managing director Shaun Day said the combined Telfer and Havieron resource had the potential to underpin a "multi-decade, world-class mining hub."

An updated ore reserve estimate for Telfer is targeted for the second quarter of 2026, with ongoing drilling focused on converting inferred material into higher-confidence categories.

More than 134,000 metres of drilling were completed during 2025, with a further 100,000 metres planned.