The explorer said the resource had the potential to be developed into a medium-sized, open cut, low-volatile PCI coal operation.
Drilling showed an aggregate seam thickness of 8.8-10.1 metres across the Phillips, Leichhardt and Vermont seams.
Norton said geological interpretation indicated the coal seams in the North and South areas were contiguous across the Sienna Central area.
The project is surrounded by major producers Macarthur Coal, Curragh, Foxleigh, BHP, German Creek and Anglo Coal.
Norton is now preparing a detailed feasibility study for Sienna.
Norton was trading down 3.3% mid-morning to 14.5c.
