The new measured resource, which is a first, at the former Anglo American mine is of 55.33 million t, grading 39.26% Fe.
The measured and indicated resource increased to 229.48 million t at 38.76% Fe, from 176.7 million t at 39.75% Fe.
The inferred mineral resource increased to 46.76 million tonnes at 36.20% Fe, from 8.7 million t at 36.9% Fe.
The results were reported within an optimized pit shell and using a cut-off grade of 25% Fe.
"The new measured resource and the overall increase in the mineral resource provides a sound basis for an initial 15-year mine life, with the potential to expand this further by upgrading the 46.76 million t of inferred resources," Cadence CEO Kiran Morzaria said.
"The main aim of our new mineral resource statement was to provide a sound basis for pre-feasibility studies. In particular, to convert a significant portion of the indicated mineral resource into the measured category. The results reported today have achieved this goal and more," Morzaria said.
He said that the higher degree of certainty in the estimate provides for more funding options.
The mine was previously majority owned by Anglo American. It produced 6.1 million t of iron ore per annum. Prior to its sale in 2012, Anglo valued its 70% stake in the project at US$866 million, or $1.2 billion on a 100% basis, and after impairment valued at $462 million, Cadence says.
Cadence owns 27% of the project, with its joint venture partner, Indo Sino Pty Ltd, owning the rest.
WH Ireland Capital Markets noted that the mineralisation at Amapa extends for about 6.5 kilometres in strike, roughly 1.5km in width, and is greater than 100 metres in depth in some places.
"The MRE at Amapa does not include the Dragao mineralized body (3.5km to the north east), which could be a potential resource upgrade," it said.
"Today's RNS is very positive for Cadence as it continues to advance the Amapa project towards restarting commercial production," it added.
Cadence's share price was up 3% day on day at 9.75p (US$0.11) at the most recent market close.
