The back side of this galena and marcasite specimen is covered by a thin druse of quartz crystals. If you look closely, you will see there is a 3-4 mm gap between the quartz druse and the marcasite, but no gap with the galena!
It looks for all the world like the marcasite has a cloak pulled over the back of its head! I think, originally, there was no gap, but there was a dissolution event with removed some of the marcasite along the junction with the quartz. A very cool geologic specimen. If anyone knows the exact mine, please send me an email. No damage and 4.5 x 3.6 x 2.5 cm.