Joint venture owners Dalrymple Resources (40%) and Canadian-listed LionOre Mining International (60%) announced eight days ago that they had already proved up a resource of 2.1 million ounces.

The expectation is that this number could swell to 2.5Moz by year-end, which is the date when another 50 reverse circulation and diamond holes are factored into the resource calculation.

Already Thunderbox is exhibiting a number of glowing traits - it appears to have high tonnes per vertical metre, the surface mineable part of the deposit will have a low strip ratio and test recoveries to date have been excellent.

At the beginning of the month Dalrymple said 54,000m of RC and diamond drilling at the Wildara joint venture had outlined a resource of 30 million tonnes at a grade of 2.2gpt of gold. The resource has been outlined over an 1800 metre strike length and down to a vertical depth of 450m.

The company said drilling had yet to close off the northern and southern strike extremities of the deposit and that there was the potential for high-grade zones at depth.

More than 80% of the resource is classified as Indicated due to the excellent internal geological and grade continuity of the mineralisation.

The boundary of the Indicated resource is fixed 60m beyond the most distal drill holes at the margins. The Inferred portion is located on the margins of the deposit where the mineralisation is extended between 40 and 60m depending on the confidence of continuation, beyond the Indicated boundary.

The resource was estimated by block modeling with the grade interpolated by the inverse distance squared method using SURPAC software.

Sampling of diamond core has been encouraging with excellent leaching and gold recovery rates. More recent test work found that the addition of oxygen in the cyanide solution substantially enhanced the leaching kinetics on the primary samples giving recoveries of 92-98% within 24 hours.

Dalrymple managing director, Marcus Harris, said Thunderbox’s potential at depth was enormous with only 5% of the holes sunk being to significant depth. He said deeper drilling would be accelerated once the open pit feasibility study was completed.

“We’re looking to ultimately develop an operation with a mine life of at least 10 years,” he said. “The development capital cost will be in the order of $40 million which means this operation will have good cash flows.

“Pre-feasibility work is already quite advanced, we have Lycopodium examining the process options, AMC doing a mine plan and Amtec looking at the metallurgy.”

To date Thunderbox’s only flaw has been the hardness of its ore, which has bond work indicies of between 21 and 25.

Harris says a solution could be to use smarter blasting and coarser grinding

“Our original metallurgical work had us grinding the ore to –75 microns,” he said. “We are now experimenting with a coarser grind which if it works will cut down power consumption. Combining that with modern blasting techniques we might not have build such a big grinding and screening circuit,” he said.

Thunderbox is well located being just 40km from Leinster in WA’s north-eastern Goldfields. The mine is also likely to benefit from the ramp-up of Ananconda Nickel’s Murrin Murrin nickel mine, with the headquarters of Stage Two slated to be located just 10km from Thunderbox.

Shares in Dalrymple have been steady at around 70c with few sellers at these levels. The WA-headquartered explorer’s top 20 accounts for about 55% of the issued shares.

Chairman Neil Tomkinson, co-director Joshua Pitt and associated friends are understood to speak for about 40% of the company.