Quality building stone
This section of cut roach stone is packed with bivalves and gastropods. Look very closely and you can also just about see the minute egg-shaped ooliths (grains) that make up Portland Stone and help create its quality as building stone. Ooliths form from grains of sand and shell fragments rolled about in a warm sea. Layers of calcium build up over them to form the spherical ‘ooid’. Portland Stone is made of millions of these minute structures, so the rock is a bit like a fish roe. This allows it to be cut or carved in any direction; an essential quality of a building stone.
The roach is a decorative stone and is also very strong, but it is less favoured by architects because of the difficulty in supplying consistent blocks with a similar texture. It was used in the rebuilding of the Cobb (the harbour) in Lyme Regis following the Great Storm of 1824. It’s also used in a very solid bench outside Euston Station in London.
