Located on the bank of the Mississippi River, in Buffalo, Scott Co., Iowa, the Linwood Mine is one of the largest underground limestone mines currently in operation in the United States. The Linwood Mine is known to produce beautiful, museum quality calcite and barite crystals. Less known is that the Linwood Mine also produces beautiful and interesting fluorescent specimens. Between 2013 and 2014, a unique find of barite was made at the Linwood Mine, producing flat tabular crystals having an etched texture with a growth pattern resembling reptilian scales, leading to the description “dragon scale barite.” These specimens show a similar bright white to blue/white fluorescence under all UV wavelengths with a strong pale blue/green afterglow following short wave and a very sharp bright green afterglow following exposure to long wave UV. The following series of photographs show an excellent example of Dragon Scale barite from this find. This specimen consists of a single, flat, etched barite crystal (dragon scale) sitting in a larger bed of small platy barite crystals.
Close-up view of a Dragon Scale barite crystal measuring 7.8 x 3.9 cm, showing bright blue/white fluorescence under long wave UV (365 nm). Note the highly textured surface of the crystal showing an etched pattern and unusual growth features.
The above gallery images show the dragon scale barite crystal under visible light (left), long wave UV (center), and phosphorescence following exposure to long wave UV (right). Click on the individual images for a larger view.
Full view, shown under visible light. This large specimen measures 19.0 x 17.3 x 11.6 cm.
Full view of specimen showing fluorescence and phosphorescence/afterglow under UV: Fluorescence under long wave UV (upper left), phosphorescence following exposure to long wave UV (upper right), fluorescence under short wave UV (lower left), and phosphorescence following exposure to short wave UV (lower right). Click on the individual images for a larger view.