What is slag in geology ?
Slag : definition
In the old exploitations, the slag and the scoria were stored with the poor ore. When these were deposited at the seaside, the action of sea salts frequently caused neoformation at their expense of mineralogical rarities, often chlorides and iodides, such as penfieldite (Pb2Cl3 (OH)) on the photo (© Gianfranco Ciccolini). The Greek Lavrion, which concealed the most important lead and silver mines of Ancient Greece, is rightly famous for its mineralogical neoformations on slag and scoria.