This maiden mineral resource for the Bramaderos gold-copper porphyry project in southern Ecuador is just the beginning, Sunstone says.

When it comes to porphyry deposits, size counts.

These multigenerational monsters are responsible for ~60 per cent of the world’s copper, most of it molybdenum, and significant amounts of gold and silver.

Their easy-mining large volumes make up for the low grades, typically between 0.3 per cent to 1 per cent copper equivalent.

Sunstone Metals’ (ASX:STM) initial resource of 156Mt at 0.53g/t AuEq (0.35g/t gold and 0.11% copper), for 2.7Mozs AuEq is from the Brama-Alba target only, and has been optimised for open pit mining.

It does not include mineralisation outlined at several other targets within the Bramaderos concession, or at El Palmar in northern Ecuador.

There is plenty of upside from here.

Sunstone Metals asx stm
Summary of potential growth options for the Bramaderos project. Further drilling on multiple opportunities is expected to significantly grow the gold and copper inventory. Pic: Supplied.

Monster exploration target

An initial Exploration Target – which is in addition to the resource – consists of between 255 and 360Mt at a grade between 0.40 and 0.74g/t AuEq2 (gold + copper) for contained metal of between 3.3Mozs and 8.6Mozs AuEq.

Sunstone managing director Malcolm Norris says Bramaderos is heading towards being a very significant project with huge potential for growth.

“The size of the metal inventory, the fact it runs from surface, and the extent of the known mineralisation which sits outside the boundaries underpins a strong future for Bramaderos and Sunstone,” he says.

“It is important to note that these estimates are just the start. We are highly confident that ongoing drilling will continue to grow the size of the opportunity.

“We can see a clear line to a 5-10Moz AuEq resource for the project and our exploration program is focussed on delivering that.”

More drilling to come

Sunstone’s goal is to grow the metal resource inventory significantly by drilling more holes at all targets including Brama-Alba extensions, Melonal, Limon, Sandia, Porotillo, Playas, and Yeso.

“We have taken a somewhat conservative approach to the Exploration Target estimate and not considered porphyry gold-copper targets at several areas where Sunstone has not yet drilled,” Norris says.

“But we will drill those areas in 2023.

“We aim to deliver a globally significant gold-copper inventory across multiple nearby targets. This has been very efficient exploration with a discovery cost of A$9/oz on a gold equivalent basis.”

Metallurgical studies positive

Meanwhile, Norris says results of preliminary metallurgical studies to produce a clean gold-copper-silver concentrate are positive and recent preliminary leach tests suggested that an even larger opportunity may present itself with leaching of low-grade material.

“Bramaderos is ideally located for a large mining development project,” he says.

“It is at ~1,000m above sea level, in proximity to the Pan-American highway, has adequate power supplies nearby from Ecuador’s hydropower grid, the project is also supported by nearby commercial airports and significant cities (Loja, population 200,000) and has a supportive community keen to benefit from all that a responsible mining development brings”.



This article was developed in collaboration with Sunstone, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.