6" x 3.5"
Interior white overlapped by a lip-dip of black glaze makes bluish. Lower exterior is the Earth crust slurry, applied to an area chattered by a managed accidental dynamic while the clay was wet and revolving on a moving wheel. Speckled band is the sediment with the iridium anomaly.
More info available by using drop-down menu of Collected Mud Stories, click on "Mid Atlantic Ridge and Cretacious Tertiary Boundary".
Thumb-well of blue sea-glass.