Limestone Limestone Limestone is a grey rock that is made of calcite. It is used as building stone, and to make concrete. The specimen on the right is Roman concrete from the Arc in York , a wonderful museum where you can handle archaeological finds.
Limestone is a sedimentary rock, made of bits dropping to the bottom of the sea.
You find lots of fossils in limestone. Calcite dissolves very easily in water, and so sea creatures can use the mineral to make their sea-shells. When they die, the shells make fossils, and in mass, limestone. This limestone then dissolves in the sea for more creatures to make sea-shells from, and so on. They are pieces of limestone cut like this, and polished to show the fossils better.