A 2.8Mt increase has taken overall resources to 19Mt at 1.15% lithium oxide, with three rigs currently in action.
Meanwhile, Piedmont is continuing scoping work - with results due in July - and is planning to complete definitive feasibility work and have permitting approvals by the end of 2019.
Earlier this month Piedmont said it was "evaluating a range of offtake, financing and strategic alternatives".
The company is led by former investment banker Keith Phillips.
Piedmont raised A$12.2 million in equity late last year by issuing new shares priced at 11c each.
Shares in the company were off 3% to 17.5c in morning trade, capitalising the company at $117 million.