ore-leaching tank - pad construction
- otavite
- otolith
- ottajanite
- ottemannite
- otter board
- ottrelite
- ouachitite
- ouadi
- ouenite
- ouklip
- oule
- oulopholite
- out of balance ores
- out to out
- out wash
- out-of-balance load
- out-of-phase component
- out-of-plane energy
- out-of-plane event
- out-of-plane imaging
- out-of-the-plane reflection
- outblowing wind
- outbreak
- outburst
- outburst cavity
- outburst hazard
- outburst intensity
- outburst of carbon dioxide
- outburst of salt
- outburst prediction
- outburst prevention
- outburst-prone
- outburst-prone seam
- outcrop
- outcrop line
- outcrop map
- outcrop migration
- outcrop mine
- outcrop mining
- outcrop of fault