Dulcote Agate 95.28 ct Oval Cabochon 65.30 x 44.30 x 4.20 mm z823

Dulcote Agate 95.28 ct Oval Cabochon 65.30 x 44.30 x 4.20 mm z823

Dulcote Quarry, near Wells, Somerset England
The agates from Dulcote Quarry in the Mendip Hills are some of the finest in Britain but are no longer being obtained since the quarry was closed many years ago.

They occurred 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.

How these nodules were formed has been the subject of debate but it is thought that they were originally composed of anhydrite, which was slowly replaced with quartz from the outside inwards, with varying amounts of hematite and other minerals creating colour banding.  Some nodules are hollow and contain crystals of quartz.