'POTATO-STONE' - Clevedon, Somerset

 
Both halves of a geode lined with quartz crystals                
 
Clevedon, North Somerset

The Mendip Hills area has yielded some beautiful quartz geodes. They occur as nodules in the red marly clays overlying the Carboniferous Limestone. These clays were laid down in an arid, tidal-flat environment during the Triassic period (200 million years ago) when Britain was situated in the tropics.

These geodes are known as a 'potato-stones' due to their external appearance.

This example is from an old collection. It was collected in 1957.