Limestone Limestone is a grey rock that is made of calcite. This piece of limestone (to the left) came from Portland Bill on the English South coast. It is used as building stone, and to make concrete. You may think that concrete is a modern building material, but it was used by the Romans! The specimen on the right is Roman concrete from the Arc museum in York. 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 if there are enough of them, limestone. This limestone then dissolves in the sea for more creatures to make sea-shells from, and so on. By the way, these aren't real eggs! They are pieces of limestone cut like this, and polished to show the fossils better. Limestone is comes from 'lime' and 'stone'. The word 'lime' is derived from German 'Leim', meaning 'glue'. Limestone made quicklime, which was used in mortar. You could say that mortar glues bricks together!

Limestone is a good building material, especially for cathedrals, since you can carve it easily. It does get eroded by being dissolved slowly by rain, especially acid rain.

Larger pictures of Limestone: