opacifier
opacity
opal
opalescence
opalescent
opaque
open
open-air
open-belt
open-burning
  open-cast
open-casting
open-cell
open-chain
open-channel
open-circuit
open-combustion-chamber
open-cut
open-cycle
open-die
open-ended

    open-cast working with adits and raises

    разработка штольнями