The project in Brazil consists of seven granted exploration licenses covering a total area of 12,997.6 hectares, divided across both the Arapua and Maximus prospects.
Potassium oxide (K2O) rich rock, had been mapped over an area of around 1,691 sq km, the firm revealed and initial metallurgical test work suggests grades can be improved by simple screening.
The firm is due to start initial air core drilling programme to validate initial drill results this month (February 2016).
Harvest's executive chairman, Brian McMaster said: "Since receiving the proceeds of our recent funding in January, the team has been very busy ground mapping the extent of the potential DANF (direct application natural fertiliser) product.
"These excellent results indicate that once we have defined a commercial product, we would have sufficient source material to support a substantial long-life project.
"The team is currently preparing the ground ahead of commencing an initial air core drill programme next week to verify the original XRF results from the auger drilling. Once this has been completed, the drill programme will be expanded to estimate a JORC resource and further more detailed metallurgical test work will be carried out to define a commercial DANF product."
Harvest shares rose 10% to 4.125p in London.