FluoriteThis delightful cube is a crystal of fluorite, the mineral made of calcium and fluorine. The

FluoriteThis delightful cube is a crystal of fluorite, the mineral made of calcium and fluorine. The structure of this mineral is cubic and it commonly grows in settings with abundant fluids, allowing it to easily grow large, well-shaped crystals.Note how the purple color, the most common color in grains of fluorite, appears and disappears in certain bands that track conditions as the crystal grew. The purple color occurs when a fluorine atom is missing from the structure and an unbound electron takes its place. Unbound electrons would balance the charge in the grain, but they sit in open spaces and thus interact with light in the visible range.These unbound electrons can be caused by radiation exposure, but it’s tough to expose a single layer in the middle of a grain to radiation. Instead, in this case it probably relates to the availability of calcium and fluorine as the crystal was growing. A layer that grows when extra calcium is available might leave missing fluorine spaces that can be filled by open electrons, creating this color pattern.-JBBImage credit: Macroscopic Solutionshttps://flic.kr/p/qm1VtJReference:http://bit.ly/25DoCQMhttp://www.galleries.com/fluoritehttp://www.mindat.org/min-1576.html -- source link
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