The inferred resource comprises 6 million tonnes of drainable sulphate of potash (SOP) with an average grade of 5080mg/l SOP, or 25Mt of total contained SOP in the brine volume.
The resource estimate was within the company's exploration target of 2.5-9Mt.
Trigg said it saw potential to expand the resource to the west where higher grades have been encountered.
It has applied for two additional tenements in the area.
Lake Rason is the most advanced of three prospects at the Laverton Links project.
"This demonstrates the excellent potential of our SOP projects and provides a solid platform for us to evaluate the broader potential of a new SOP production hub centred on our Lake Throssell discovery, with Lake Rason likely to become a satellite or feeder project to what appears to be the higher-grade proposition at Lake Throssell to the north," Trigg managing director Keren Paterson said.
"To that end, we are currently preparing for a major new aircore drilling program to further evaluate the Lake Throssell project, with drilling targeted to commence next quarter."
Lake Throssell sits to the northwest of Laverton Links, just to the north of Gold Fields and Gold Road Resources' Gruyere gold mine.
Results for 18 hand auger samples reported late last year had an average grade of 5296mg/l.
The company is targeting a maiden resource for Lake Throssell in the September quarter.
Trigg listed on the ASX in October 2019 after a A$4.5 million initial public offering and had $2.7 million at the end of December.
The company was the worst-performing mining IPO of 2019, immediately losing 30% on its first day of trade.
The stock has continued to decline, falling to a low of 4.1c last week, 79.5% below the 20c issue price.
Shares in Trigg rose 4.7% today to 4.4c.