Fluorite Opal some with highlights of purple

some with highlights of purple or blue around the outer edges

and blues as well as the more commonly encountered clear or pale white

or the formation of equally thin layers of secondary minerals due to hydrothermal or other alteration

Calcite is clear naturally but it can be found in a variety of brilliant colors due to the presence of chemical impurities during formation

Fluorite Opal some with highlights of purpleFluorite is one of the most variable of all crystalline minerals, occurring in shades of blue, green, purple, red and many other colors corresponding to their physical makeup and conditions when the mineral was formed. The name fluorite comes from its use as a flux, or chemical cleaning agent, in iron smelting and other metallurgy. Pure fluorite is clear, but most specimens have vivid color due to various impurities and are often fluorescent. With a