According to preliminary estimates before exploration, total extractable reserve assessed by the coal ministry was about 1,000 million tonne from these two mines. But after preparation of geological reports, it was found that total extractable reserves from both the blocks will just be 500 million tonne because of difficult geo-mining conditions.

Source : The Economic Times

Link : https://economictimes.indiatimes.com/industry/indl-goods/svs/metals-mining/coal-india-arm-to-see-viability-of-merger-of-ntpcs-two-mines-in-chhattisgarh/articleshow/76003809.cms