Highfield has measured and indicated resources of 235 million tonnes grading 12.3% potash and 32.6Mt of inferred resources grading 12.9% potash at its Muga project in Spain.
Highfield said an update on the proposed project is being finalised and will be released "shortly".
The company is currently also going through the permitting process in Spain.
Highfield is backed by Owen Hegarty's private equity firm EMR Capital.
As of June 30, it had cash of A$60 million.
Shares in Highfield were unchanged at 63c in morning trade, capitalising the company at $207 million.
The stock has declined from levels around $1.10 per share over the course of 2018.