Galileo Mining (ASX:GAL) has joined Chalice Mining (ASX:CHN) in outlining a new style of metal deposit in Western Australia, featuring areas of mineralisation with a significant presence of precious industrial metals such as palladium and platinum, along with gold, copper, and nickel.

Although Callisto is smaller in scale compared to Chalice's Gonneville find, Galileo expresses confidence in discovering similar deposits in and around the Norseman area of Western Australia.

In a filing with the ASX on Monday, the company shared its initial estimate of the size of the Callisto PGE-nickel-copper deposit near Norseman in the Western Australian gold fields.

The company stated on Monday that "the Callisto discovery is the first deposit of its type identified in Australia and is analogous in mineralisation style to the Platreef deposits found in South Africa." This news led to a 17% surge in the company's shares during the first hour of trading on a quiet holiday Monday in some states.

The company is primarily owned by billionaire prospector Mark Creasy, who holds a 24.6% stake, while IGO holds an 8.9% stake. Creasy also owns a 9.6% stake in IGO. Galileo's market value stands at just over $68 million, in stark contrast to the nearly $12 billion IGO.

Galileo reported that Callisto has a "maiden Indicated and Inferred Mineral Resource Estimate of 17.5 million tonnes @ 1.04g/t 4E (4E = Palladium (Pd) + Platinum (Pt) + Gold (Au) + Rhodium (Rh)), 0.20% Ni (nickel), 0.16% Cu (copper) at a 2.3 grams to the tonne palladium equivalent (which is a way of estimating the contained metals in the deposit in terms of the dominant mineral, in this case palladium)."

Based on this estimate, the initial calculation for contained metals is 585,000 ounces of 4E (Palladium (Pd) + Platinum (Pt) + Gold (Au) + Rhodium (Rh)), 35,000 tonnes of nickel, and 28,000 tonnes of copper.

The nature of the Callisto deposit differs significantly from the massive mineralisation at Gonneville, Chalice's first discovery at its Julimar prospect northeast of Perth. Gonneville surpasses Callisto in terms of resource size and contained metals and also includes cobalt, which Callisto lacks, but it features the rare rhodium.

Nevertheless, the company believes it can expand this discovery and find similar instances of mineralisation in and around the Callisto find.

Galileo CEO Brad Underwood stated in the ASX filing that "the discovery of the Callisto deposit has been a major breakthrough in understanding the geology and prospectivity at our Norseman project."

"We have now defined a significant resource from a total of 147 drill holes (38,695m) within an established mining district of Western Australia. The discovery occurs on a granted Mining Lease just 15 km from the town of Norseman and with extensive nearby infrastructure, including a gas pipeline, water pipeline, railway, and sealed highway.

"The nature of the mineralisation at Callisto is analogous to the Platreef deposits in South Africa, where several deposits occur over a strike length of tens of kilometers. Applying this knowledge, we will broaden our search for more discoveries, starting with the prospective areas at our North and South Callisto prospects.

"Ultimately, we believe this search space will encompass the full 20 km of the prospective host rocks at the Callisto trend and the further 12 km of prospective strike length at the Mission Sill prospect, where similar geology has been intersected in drilling."