united states mine rescue association Mine Disasters in the United States
Quarry of Three Forks Explosion Portland Cement Company
Trident, Montana July 17, 1917 No. Killed - 8
An accidental explosion of 41 kegs of black blasting powder occurred on the track bench at the quarry. One man was killed instantly, and seven others died from severe burns.
The men were opening kegs of black blasting powder (supposedly with sharpened wooden pick handles and a machinist's hammer) and emptying the contents into cement sacks. The sacks of powder were then carried into a small tunnel, which was being loaded preparatory to blasting the quarry face.
No one was able to give any definite reason for the accident, and evidence adduced was not sufficient to determine definitely the cause of the explosion.
Historical Summary of Mine Disasters in the United States, Volume III