Limestone
A rock consisting chiefly of calcium carbonate, usually an accumulation of organic remains such as shells.
Marble
Limestone crystallized by metamorphism.
Metamorphose
To change into a different form, such as changing sedimentary rock (limestone) into a metamorphic rock (marble).
Moonmilk
A rare form of hydromagnesite or calcium carbonate which is semisolid.
Phreatic zone
The region, below the water table, in which rock is saturated with water.