Wulfenite - lead molybdate (PbMoO4) and mimetite (Pb5(AsO4)3Cl) on barite (BaSO4). This specimen was dug a few years ago by a friend of mine at the famous Rowley mine at Theba, Arizona. Wulfenite forms extraordinarily beautiful bladed crystal clusters, often in vivid shades of reddish-orange or yellow-orange. The smaller, rounded crystals at the base of the Wulfenite blades are likely mimetite, a lead arsenate chloride that often co-occurs with wulfenite at this location, though mimetite from this mine is usually more yellow and spindly. The larger rock on which both crystals occur is barite, or barium sulfate. Because these are heavy metal rich rocks containing arsenic and lead, despite their beauty, they are not suitable for young children, and it is probably smart to wash your hands after handling them in your collection. These crystals are also quite delicate, and require special care in display. Mimetite, in particular, is easily crushed to a fine powder, as a friend pointing at one of my best specimens once accidentally demonstrated. If you would like to learn more about any of these minerals or about the mine from which they came, here are a few links: the wikipedia page for wulfenite is particularly good: https://en.wikipedia.org/wiki/Wulfenite and here is some information on the Rowley Mine: http://www.mindat.org/loc-3352.html Here is the wikipedia page for mimetite: http://en.wikipedia.org/wiki/Mimetite and here are the webmineral.com and Wikipedia links for barite: http://www.webmineral.com/data/Barite.shtml#.U8kevWdOXIU and http://en.wikipedia.org/wiki/Barite
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