Limestone
Limestone is a sedimentary
rock composed largely of the minerals calcite and aragonite, which are
different crystal forms of calcium carbonate. Many limestones are composed from
skeletal fragments of marine organisms such as coral or foraminifera, which is
a species of marine plankton. Limestone makes up about 10% of the total volume
of all sedimentary rocks on Earth. The solubility of limestone in water and
weak acid solutions leads to karst landscapes, in which water erodes the
limestone over thousands to millions of years. Most cave systems are through
limestone bedrock. Limestone has numerous uses, including as building material,
as aggregate to form the base of roads, as white pigment or filler in products
such as toothpaste or paints, and as a chemical feedstock. During regional
metamorphism that occurs during the mountain building process, limestone
recrystallizes into marble.
