A mining explorer says an area close to Darwin appears to be rich in uranium.

Thundelarra Exploration is expanding its drilling program in the Pine Creek region, 200 kilometres south of Darwin.

Company exploration director Brian Richardson says recent results have changed the belief that the area is not worth mining.

"We have changed it by finding this blind, exceptionally high-grade mineralisation, uranium mineralisation, in an area that previous explorers had looked at back in the uranium booms of the 70s and early 80s," he said.

"But they had really discounted the whole region."

He says the company has found good grades of uranium in unusual deposits in the region.

"This style, which sits on anticlines, is exactly the same as most of gold deposits in the Pine Creek area," he said.

"It is really significant because it opens up a large area of ground that was previously under or unexplored for uranium."