4.5" high x 3.5" wide
Mid-Atlantic Ridge rock slurry on porcelain clay, applied by dipping the bottom two-thirds into the Earth’s crust slurry that was then brushed off when wet. Sometimes light shines thru the clay wall.
Shiny brown interior is an Albany-slip (once mined in NY state) glaze that has some Red Sea sediment added for color. Top third is another glaze assembled from refined materials. Sea-glass in the thumb well.