bituminous
black
central
clean
coal
coal burning
cube
dark
deposits
ecology
effect
energy
environment
extract
extraction
fuel
fuels
gas
heat
heating
helmet
hot
industry
lignite
load
loading
manufacturing
material
metallurgical
mine
miner
mineral
mines
nature
pile
power
power station
resources
safety
safety helmet
stone
things
tools
types
uses of
yellow helmet