ore-leaching tank - pad construction
- orthoandesite
- orthoantigorite
- orthoaxis
- orthobituminous
- orthobituminous coal
- orthoceracone
- orthoceraconic
- orthoceratites
- orthochamosite
- orthochem
- orthochlorite
- orthochoanitic
- orthochronology
- orthochrysotile
- orthoclase
- orthoclase feldspar
- orthoclase feldspars
- orthoclase porphyre
- orthoclasite
- orthoclastic