The results from the first hole and top 200m of the second have identified zones of higher-grade gold and copper within a large, lower-grade porphyry gold-copper system, Cornerstone said.
A highlight included 96.6m at 0.61g/t gold, 0.18% Cu and 2.08g/t silver from 39.3m in the first hole.
"We've only drilled two holes, but we can already see clear opportunity for a sizeable gold-copper system extending from surface outcrop to at least 300m below surface, and with opportunity to extend laterally by in excess of 500m," exploration vice president Yvan Crepeau said.
Drilling at the Limon prospect earlier this year had intersected wide porphyry mineralisation.
Sunstone Metals (ASX: STM) is earning into Bramaderos and can earn an initial 51% of the project by spending US$3.4 million over three years on a phase one drill programme, under a deal struck in mid-2017.
Sunstone said yesterday it was well-funded to accelerate drilling at Bramaderos, with a fully underwritten options exercise this month set to deliver A$4.6 million (US$3.1 million).
Cornerstone has other exploration assets in Ecuador including a 15% stake in the Cascabel gold-copper project, majority owned by SolGold.
Shares in Cornerstone and Sunstone are down 43.3% and 4.2% respectively year-to-date and the companies are capitalised at C$108.8 million (US$81.7 million) and A$28.2 million (US$19 million).