Truly wonderful agate geode with millions of years old water bubble moving about in its cavity. The bubble you can see moving is in the middle of the crystal window in the middle of the polished face - it measures about 0.7cm.
Enhydros are formed when water rich in silica percolates through volcanic rock, forming layers of deposited mineral. As layers build up, the mineral forms a cavity in which the water becomes trapped.
The cavity is then layered with the silica-rich water, forming its shell. This measures about 3.8cm x 7.5cm 6.5cm.