Get out your crowbars, Sunstone Metals (ASX:STM) is about to prise open the core of a potentially big copper-gold porphyry system in Ecuador.

The company revealed today results from a second hole at the Limon prospect, part of the larger Bramaderos project, delivered a hit of 267m at 0.05 grams per tonne (g/t) gold, 750 parts per million (ppm) – or 0.08 per cent — copper and 22ppm molybdenum.

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This includes a 14m intercept at the bottom of the hole that recorded 0.1g/t gold, 0.2 per cent copper and 41ppm molybdenum.

“We believe we have drilled very close to a significant porphyry system at Limon and now have confidence in where the next hole should be drilled,” managing director Malcolm Norris said.

Investors did not like the grades, sending the stock plunging 20 per cent on Tuesday morning.

What is a porphyry?

A porphyry deposit is hosted in a type of granite rock, the same as most of the major copper deposits around the world.

These deposits are usually large and low-grade but can be mined at low cost due to their scale.

Globally, over 60 per cent of copper, all of the world’s molybdenum, 10-15 per cent of uranium and a significant amount of gold comes from porphyry deposits.

Porphyries typically range from 100 million to 5 billion tonnes, but at lower grades of between 0.2 per cent and less than 1 per cent copper.

So much… mineralisation

Sunstone has also discovered that mineralisation continues down to more than 600m after drilling its first hole at the Bramaderos Main prospect, which lies 2.5km south-west of the Limon prospect.

The hole was drilled down to 669.45m, below a previous drill hole that returned a hit of 248.1m at 0.56g/t gold and 0.14 per cent copper from 9.1m to the end of the hole.

“We are seeing grades at Bramaderos Main that are comparable to other porphyry deposits such as Cadia in NSW and our goal is now to extend the area of mineralisation,” Norris said.

Sunstone is now drilling a second hole into the Bramaderos Main prospect, 120m to the south of the first hole, and expects first results in late July.

In other base metals news:

Raiden Resources (ASX:RDN) also thinks it may have uncovered a porphyry system at its Donje Nevlje project in southern Serbia.

“Despite only three drill holes being completed in the initial round of drilling, the company intercepted copper and gold mineralisation at depth,” managing director Dusko Ljubojevic told investors. According to Raiden, the mineralisation is possibly related to a deeper porphyry system.

Gindalbie Metals’ (ASX:GBG) copper spinout Coda Minerals has received a request from shareholder Sandon Capital to consider potential liquidity options. Coda is planning to list on the ASX as soon as possible on completion of the demerger.

Gindalbie said the Coda board would explore potential liquidity options for the unlisted Coda shares in an “equitable and timely manner”.

Alaska-focused copper-gold explorer PolarX (ASX:PXX) has raised $3.4m from a recent rights issue. The company has boosted its coffers to over $7.5m, which PolarX said meant it was fully funded for its exploration programs, including drilling planned at its Saturn, Zackly and potentially Mars prospects.

Zinc explorer Superior Lake (ASX:SUP) has appointed experienced advisor Jay Gow to assist it with offtake negotiations. The company said Gow’s appointment followed significant interest from numerous global metal traders and smelters regarding the zinc concentrate from its Superior Lake project in western Ontario, Canada.

Tempus Resources’ (ASX:TMR) chief operating officer – Latin America, Rodrigo Izurieta, has been elected as a principal director of the Chamber of Mines of Ecuador. Izurieta will be joined on the board of the Chamber of Mines by representatives from other mining companies active in Ecuador, including BHP (ASX:BHP), Newcrest Mining (ASX:NCM), Lundin Gold, Solgold and Codelco.