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A brightly fluorescent calcite scalenohedron crystal enclosed in a non-fluorescent calcite matrix. The formation of this specimen causes the internal calcite to have a zoned diamond shape.
These types of complex specimens are formed by multiple generations of calcite growth and manganese oxide minerals, with the end result producing a brightly fluorescent central calcite scalenohedron, encased in layers of essentially non-fluorescent calcite and outlined in black manganese oxide.
Color zoning can be created by changes in the nature of the fluid from which the crystal is growing. The changes could be due to temperature, pressure, and/or chemical changes. In the case of fluorescent zoning, there can be a change in the activator (what causes fluorescence) that is incorporated in the growing crystal. Source: UV Waves, v50 n6, Glenn Waychunas
The Garpenberg mine is located in Bergslagen, a very old mining area in the southern part of Sweden.
The mine is very active today and is one of Europe's most progressive underground mining operations. Collecting is not possible, and the few specimens that reach collector's hands are highly prized. The mineralogy is quite similar to that of Franklin NJ.
