This unique fluorescent specimen comes from the Palmarejo Mine, in Chínipas, Chihuahua, Mexico, and consists of a brightly fluorescent calcite scalenohedron encased in a non-fluorescent calcite fishtail twin crystal. Under short and mid wave UV the internal calcite scalenohedron fluoresces bright red/orange. The fluorescent scalenohedron can be clearly seen in cross section where the specimen is cleaved at the base, producing a distinct fluorescent diamond shape surrounded by non-fluorescent calcite. This complex specimen was formed by multiple generations of growth of calcite 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. The size of this piece is 11.9 x 9.2 x 6.3 cm, and it weighs 803 grams.
As shown in the photograph above, taken under short wave UV (254 nm), the fluorescent scalenohedron can be clearly seen in cross section where the specimen is cleaved at the base, producing a distinct fluorescent diamond shape. A similar response is also seen under mid wave UV (302 nm), not shown.
Same view as shown above, seen under visible light here. From this angle, the cleaved surface of the base of the twin crystals is seen, revealing the internal calcite scalenohedron in cross-section.
Full view of the same specimen, taken under short wave UV (254 nm). The brightly fluorescent cross section of the internal scalenohedron can be seen at lower right and the rest of the crystal glows dimly through the translucent calcite twin, within which it is encased.
Full view of specimen, shown under visible light. Note the fishtail twin calcite crystals seen at upper left.
Although the Palmarejo gold and silver mine dates back to the early 1800s, its production of these unique calcite specimens did not begin until approximately 2012.