This curious oddity is a fluorescent drill core specimen that was sampled from an Ordovician limestone bed on the West side of Nashville, Tennessee. The limestone is from the Fernvale member of the Sequatchie Formation, which is unique due to its karstic nature with lots of voids and small conduits which tend to trap petroleum. It is the petroleum that has permeated into the porous voids in the limestone that provides the fluorescent response under UV. This drill core specimen measures 68 mm in length and has a 47 mm circular diameter.
In the photograph above, the drill core shows a bright, multi-colored, fluorescent response under full-wave UV (SW/254nm + MW/302nm + LW/365nm). The fluorescence is caused by petroleum and hydrocarbons that have permeated into the porous Fernvale limestone. The fluorescent response is similar under all UV wavelengths with only subtle differences in the color and brightness.
The same drill core specimen shown under visible light.