Vanadinite shares the same structure with Apatite and the two share similar crystal shapes at times. Vanadinite is part of a chemical series with two other minerals; Pyromorphite (Pb5(PO4)3Cl) and Mimetite (Pb5(AsO4)3Cl). Vanadinite is separated from pyromorphite and mimetite by its blowpipe reactions. Take a look at the close up picture. This specimen has lots of hopper crystals . This is an old specimen from Arizona.