Bioclastic, oyster-bound clasts of well-cemented patch reef in a matrix of shelly oosparite – Many large grey and white oyster shell fragments. Patch reefs were formed by masses of oysters and bryozoans cemented around a massive calcareous laminated framework built of the red alga Solenopora.
The shells are randomly distributed throughout the stone.
Texture is typically coarse with some vuggy patches.
Typical Portland colour - variable light to dark grey, the colour varying with the density of included shell.