room conveyer - sand-clay matrix
- rugged
- rugged area
- rugged case
- rugged housing
- rugged relief
- rugged terrain
- rugged topography
- ruggedness
- rugose
- rugose coral
- rugosity
- rugulate
- ruin
- ruin agate
- ruin marble
- ruinous earthquakes
- rule
- rule-of-thumb method
- ruler
- rules of mines, placers and shafts development in nonferrous, rare and precious metals