Wulfenite is a favorite of high-end mineral collectors. Every year, the largest mineral show on Earth, the Tucson Mineral Show in Arizona, picks a theme mineral, and wulfenite is popular enough that it was the theme mineral for the show in 2019. It’s also the Arizona state mineral, as of 2017. Wulfenite can be yellow, brown, green, and other colors, but the ideal color is a reddish orange. Of course, wulfenite, like all minerals, belongs to a specific mineral system (tetragonal), but for collectors its ideal shape is when a single “windowpane” crystal is standing on a piece of rock and barely connected at the base. Windowpane crystals are square and can be thin enough that you can see clearly through them. Be careful, though, wulfenite is only a 3 or so on the Mohs hardness scale, so it can be easy to break such crystals, like a standard glass window. You can find wulfenite in and around lead mines (since lead is its main ingredient), along with minerals like cerussite and pyromorphite. But the fact that it contains the element molybdenum (muh-lib-den-um) (Mo) makes it special, as well as putting it in the class “molybdates,” and there are not very many of those!