Scainiite is a very rare lead-antimony sulfide. The mineral was known only in a few, poor specimens from this locality until recently (I am told these were collected in 2009), as you can see from the few photos of smears on a rock, shown on MINDAT. Even at its type locality, 3 mm crystals would be considered large. Here you have, however, 4 cm-long flatlaying crystals on matrix. They are embedded, and grown in aggregate, but still are huge examples of the species and this is one of the more rich specimens recovered.