Blankenship served time in prison for safety violations connected to a 2010 disaster that killed 29 miners and is seen as the weakest of the three candidates in the upcoming primary.
Amid concerns Indonesia could exhaust existing minable coal reserves of 13 billion tonnes 25 years, the government is considering measures to push miners to carry out exploration work before they can obtain permits to increase output.
The smelter, which produces some 430,000 metric tonnes of aluminum annually, has been operating at reduced capacity by non-union workers since Jan. 11.