Museum quality, Fresh water precambrian stromatolite!
on back t is natural wind eroded surface!
José-Javier Alvaro, Hassan Ezzouhairi et all; Alkaline lake systems with stromatolitic shorelines in the Ediacaran volcanosedimentary Ouarzazate Supergroup, Anti-Atlas, Morocco Precambrian Research 179(1):22-36 · May 2010