Calcite Crystals on Limestone Matrix, Linwood Mine, Buffalo, Scott Co., Iowa

Gemmy, modified scalenohedral, calcite crystals with marcasite inclusions, on limestone matrix, from the Linwood Mine, Buffalo, Scott County, Iowa. This specimen shows an interesting multi-wavelength fluorescent response under UV. Under short wave UV the calcite shows moderate, pastel, pink fluorescence with isolated brighter white zones within some of the crystals. The limestone matrix is also dimly fluorescent. After the short wave source is removed, brief blue and white phosphorescence is seen, highly zonal in nature. Under long wave UV the calcite shows a very dim pink response, but the zoned areas that responded white to short wave UV now fluoresce brighter white. The white fluorescent regions correspond to internal brown areas near the base of the crystals that can be seen under visible light. This suggests that the white fluorescence is caused by the presence of an organic activator. The pink fluorescence is likely due to an inorganic activator, perhaps manganese/lead. This specimen measures 13.2 x 11.0 x 8.2 cm.

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