This stone is part of a meterorite that fragmented and fell near Tataouine, Tunisia, in 1931. It's made up largely of a green mineral called Diogenite, and is thought to have originated within the asteroid Vesta. Source.
Farmers in Ghar El Melh cultivate the sandy shore, relying on fresh water flowing off the nearby hills to the sea on top of the briny water table. Source.