Pyrite

These razor sharp Pyrite specimens have been prolifically produced since 1976. They form in cliffs of marly matrix and are blasted free. In most cases the loose cubes and clusters are then married back to the matrix with some bonding glue. Occasionally, interpenetrate cubes form chains or series which require no repair. This cluster of about a dozen cubes is perfection. Ex Mike Wortham

Locality: near Navajun, La Rioja Spain

Composition: iron disulfide