From the type locality for the species, this specimen of herbertsmithite is large and showy. Herbertsmithite is a copper zinc hydroxychloride and is a member of the Atacamite Group, although it has a highly unusual crystal structure and is intensely in demand by science labs for study. Ex. Paulo Matioli collection. An example of the literature can be found by Googling, and you get such articles as " Herbertsmithite and the Search for the Quantum Spin Liquid." I have not had a rich piece of this size and quality since the find of 2007, from which this presumably came.