Portland rocks – geological abstract art

The Isle of Portland in Dorset, which is part of the Jurassic Coast World Heritage Site, is famous for its limestone. Rock has been quarried here for thousands of years. There is evidence for Portland’s ancient quarrying and stone masonary industry everywhere.

The massive blocks and strata feature all around the coast as well as in the actively worked and disused quarries inland. Whilst the stone is generally pale in colour, there are areas where the rock has undergone a colourful transformation. This can happen when rainwater percolates the surface soil and trickles down through the calcium carbonate limestone bedrock, dissolving some of the calcium. Iron and other minerals can also enter the solution – giving it colour. The resulting liquid then seeps out between the strata in the cliffs and runs down the rock face. As the water evaporates, the calcium and other minerals are precipitated as coloured calcite – in much the same way that stalagmites and stalagtites are formed in caves. However, here on the Portland rock faces, a crystalline coating is formed that can take the form of either a continuous sheet of varying textures and hues or a series of three-dimensional ‘tears’ and trickles.

The end products of this precipitation activity are highly patterned, coloured and textured effects – designs that to my eye are nature’s own geological abstract patterns.

COPYRIGHT JESSICA WINDER 2011

All Rights Reserved