Purbeck stone is a Jurassic sedimentary limestone about 125 million years old. It is hard and takes a beautiful polish to reveal the varied colours and shell formations of each stratum.
It occurs in relatively small block sizes - some blocks only a few inches thick and four or five feet long at their longest point. Even the thicker beds are rarely thicker than eight inches. Nevertheless small is often beautiful, for Purbeck boasts an unusually varied range of decorative beds of stone.
The best known are as follows:-
Purbeck Marble Although it is technically not a marble it has been so called since it was first used in churches both here and on the continent in the twelfth century. Colours range from blue charcoal to green grey sometimes with a reddish tinge. The fossils in this stone are small and unbroken and very densely packed. It is the aristocrat of Dorset stone.
Grub Overall grey brown with a mass of fossils, which are broken, but clearly distinguishable to produce a very handsome effect when polished.
Thornback Honey coloured with a mass of small shells which contain flecks of black.
Spangle Light brown with a large spaced out shell structure, which sometimes includes dinosaur footprints and ammonites.
Cap One of the hardest of the Purbeck beds. It takes a beautiful polish and is available in larger block sizes than the others and has an interesting range of swirling blue grey colours and occasional black patches of flint and some thin calcite lines. The only stone in the group to have no fossils.
These sample images give an indication of colour and surface but there is great variety across individual pieces.