The circuit will also entail a gravity component.
The processing route chosen takes into account the refractory nature of some of the mineralisation at the current 10.6 million-ounce venture.
A prefeasibility study due for completion next quarter will reveal the key indicative numbers awaited by the market.
De Grey started the current quarter with A$97 million cash.
Shares in De Grey were up 3% to 98c in morning trade, capitalising the company at just under $1.4 billion.