In this specimen, we observed some sulfide aggregates very characteristic of Las Cruces mine. They were partially covered with calcite and under it appear groups of very brilliant chalcocite crystals. But the most interesting part of this specimen are the small, very brilliant crystals those cover sulphides. It is an unusual species: Luzonite. Luzonite is a rare copper sulfoarsenide. I have made the relevant analysis that yields consistent results: S 35.19%, Cu 41.82%, As 22.99% (%wt). You can find more information at espiadellabo.com.