(n.) A rock consisting chiefly of calcium carbonate or carbonate of lime. It sometimes contains also magnesium carbonate, and is then called magnesian or dolomitic limestone. Crystalline limestone is called marble.

aa abyssal rock bedrock block lava brash breccia conglomerate crag druid stone festooned pahoehoe gneiss granite igneous rock lava limestone living rock magma mantlerock metamorphic rock monolith pahoehoe pillow lava porphyry pudding stone regolith rock ropy lava rubble rubblestone sandstone sarsen schist scoria scree sedimentary rock shelly pahoehoe stone talus tufa tuff