The miners will work for the two mines the company will reopen, which includes the Coal Mountain mine in Wyoming and Red Fox mine in McDowell counties in southern West Virginia.
UMWA International president Cecil E. Roberts said: "At a time when the coal industry and the people who work in it are suffering, this is extremely good news.
"I appreciate the efforts of Bluestone’s owner, Jim Justice, to get these mines back up and running and to put UMWA members back to work."
In May 2009, Justice sold both mines to Russian coal producing company Mechel OAO in a deal worth $436m, and later repurchased them in February 2015.
Under the acquisition, Justice bought multiple mining sites in two counties, in addition to four cleaning plant complexes.
The two mines are said to have been idled for more than a year.