A ROOF BOLTER OPERATOR WAS MIXING RESIN DURING INSTALLATION OF A ROOF BOLT. AS HE SPUN THE BOLT, THE HEAD WAS PUSHED AGAINST THE PLATE HARD ENOUGH TO PRODUCE SPARKS. AS THE SPARKS HIT THE ROOF A BLUE FLAME WAS OBSERVED BY THE OPERATOR. THE FLAME SELF-EXTINGUISHED. MANAGEMENT DID NOT LEARN OF THIS INCIDENT UNTIL 8/27/02.