These brochantite crystals are from the Kipushi Mine in Kipushi, Shaba (Katanga) Province, Democratic Republic of the Congo. Over eighty different mineral species have been identified at this Zn-Pb-Cu mine including brochantite. It is a secondary copper sulfate containing the elements Cu, S, O and H. This piece consists of a matrix with an exposed vug that is filled with brochantite crystals. The crystals range in size from silken to prismatic. They are opaque to translucent and are green to emerald in color. This piece measures 3 x 1 3/4 x 2 inches or 76 x 45 x 50 mm.