Altamira had signed the deal with MetalStream in April, to fund the construction of a small mine and 1000 tonne per day processing plant at its Cajueiro project in Brazil's Mato Grosso state.

"To date, MetalStream has failed to make any of its contractual payments to Altamira," the company said on Friday.

MetalStream is a private company registered in Malaysia and has not commented further on the deal since announcing the agreement in April.

Altamira said it had not formally agreed to any further extensions of the MetalStream payments beyond July 14 and September 14.

President and CEO Michael Bennett, who is Altamira's largest shareholder, said the situation was very disappointing but the company had not yet made a decision to terminate the MetalStream deal.

"However, the ability to terminate the agreement presents an opportunity for Altamira to explore a number of alternative unsolicited offers of financing," he said.

"Management has made significant advances in completing the necessary engineering and design work at Cajueiro over the last few months, and is confident that these advances will increase the likelihood that the company will be able to secure funding for this project."

Cajueiro has an indicated 5.66 million tonne resource at 1.02g/t gold for 185,000 ounces and an inferred 12.66Mt at 1.26g/t for 515,000oz.

The company pointed out a production decision had not been based on a feasibility study.

It received key permits for the trial mining project over the past year and had been hoping to start production in the second half of 2021, according to an August presentation.

Altamira last raised C$1.7 million in an oversubscribed placement priced at 6c per unit which closed in March.

Its shares (TSXV: ALTA) have ranged from C3.5c-18.5c over the 12 months to date.

They closed down 3.3% to 14.5c on Friday, valuing it at $14.4 million (US$10.8 million).