background
black
black background
black gold
board
bucket
carbon
carbon dioxide
charcoal
coal
coal pile
coal structure
combustible
dark
deposits
dust filter
dust mask
energy
energy source
energy storage
exploitation
extraction
filter mask
fossil
fossil fuel
fuel
gas mask
hammer
hard
industrial
industry
lump
metal bucket
metal buckle
mine
mineral
mining
night
pickaxe
pollution
potential
raw material
shale
solid fuel
stone
to be burned
unclean
underground
wealth
wooden box