The company noted that the updated estimate also increased the average grade for measured, indicated and inferred resources.
Century and Augyva Mining Resources Inc. (CVE:AUV) are joint venture partners on the Duncan Lake project, and since the last resource estimate in 2010, Century has drilled an additional 44,007 metres of core in 125 drill holes.
At a 16-per-cent iron cutoff, the updated independent mineral resource estimate now includes a defined 1.05 billion tonnes of measured and indicated at a grade of 24.4 per cent iron, compared to a previously reported 31.3 million tonnes at a grade of 23.7 per cent iron in 2010.
Additionally, inferred resources are now estimated at 563 million tonnes grading 24.7 per cent iron, compared to a previously reported 821 million tonnes at a grade of 24.6 per cent iron.
"We are extremely pleased with this new resource estimate update for Duncan Lake, which has in excess of one billion tonnes in the measured and indicated categories, representing over 30 times more than the resource estimate of same categories in the last NI43-101 report," said Century president and CEO Sandy Chim.
"There is also a substantial resource tonnage of over half a billion in the inferred category. The completion of each successive drill program has resulted in this very substantial improvement and increase in the mineral resource estimate, while continuing to confirm consistent grades."
Century said that the updated estimate adds "solid fundamentals" that underline the potential and value of the Duncan Lake project.
"The new mineral resources will form a sound basis for the preliminary economic assessment (PEA) being prepared by Met-Chem, which is targeting an annual production of 12 million pellet tonnes at better than 67 per cent iron grade and with all other elements within commercial specification," said Chim, adding that the PEA is targeted for about year-end.
Century noted that the mineral resource estimate for Duncan Lake was based on 9,178 assays collected from 54,467 metres of drilling in 177 drill holes.
The company said that chemical analysis established that, on average, the iron formation at Duncan Lake contains very low levels of deleterious elements, in particular 0.02m per cent phosphorus, 0.03 per cent manganese and 0.23 per cent magnesium.
The Duncan Lake property is located around 570 kilometres north of Matagami, Québec. Century said the property has recently been expanded to 534 exploration claims covering 25,605 hectares.
Earlier this month, the company released the final report from phase II drilling at the property. In total, 176 holes were drilled for 54,306 metres.
Among the highlights in the most recent assays, drill hole DUN 11-237B intersected 24.64 per cent total iron over 142.9 metres and drill hole DUN 11- 352 returned 25.55 per cent total iron over 321.25 metres.
Duncan Lake is subject to a joint venture agreement between Century, which holds a 51-per-cent interest, and Augyva, which holds a 49-per-cent interest.
Century has the option to increase its interest in the property to 65 per cent, by spending $14 million by 2014.
Century Iron is Canada's largest holder of iron ore land claims, with interests in Quebec and Newfoundland and Labrador.
Along with the Duncan Lake project, the company currently has the option to acquire up to a 60-per-cent interest in the Attikamagen project under an option and joint venture agreement with Champion Minerals Inc. (TSE:CHM).