Coal blocks allocation controversy saw its flames reaching high offices like PMO, besides stalling Parliament sessions and the CBI filing charges against likes of Birla empire scion Kumar Mangalam Birla.
The scam also saw CIL remaining tangled in fuel supply row with power majors in 2013.
Lok Sabha and Rajya Sabha both were rocked during various sessions with opposition BJP demanding Prime Minister Manmohan Singh's resignation for allotment of mines without auction during 2006-09 when he also held coal portfolio.
Government also came under sharp attack on the issue of crucial files of Coal ministry going missing, with the Opposition demanding an impartial probe into it.
Under intense pressure, Coal Minister Sriprakash Jaiswal who admitted that crucial files and documents were missing, had to announce constitution of search teams to locate the same against a background where the Supreme Court set a deadline for handing over the same to the CBI.
The sector witnessed a high-decibel drama in October again when CBI lodged a case against industrialist Kumar Mangalam Birla and former Coal Secretary P C Parakh on charges of criminal conspiracy and corruption in connection with alleged irregularities in allocation of coal blocks, eight years back.
However, Birla, who drew all round support from the industry and some ministries, rubbished CBI charges against him while Parkah dubbed the allegations against him as baseless and said Prime Minister was the final decision maker and must be counted as a "conspirator", which prompted BJP to demand a through probe.
The case involving Birla created a political furore and led to a renewed demand by the opposition for the Prime Minister's resignation leading to breaking of silence by the Prime Minister's Office which rejected any criminality in the controversial allocation of coal block to Hindalco.
The sector also made headlines when MP Naveen Jindal and former Minister of State for Coal Dasari Narayana Rao were accused of alleged cheating and graft by CBI in its FIR in the coal scam.
The government watchdog CAG last year had estimated a Rs 1.86 lakh crore presumptive loss to the exchequer on account of allotment of 57 coal blocks without competitive bidding.
It was during