Colorless to greenish, transparent, glassy bubbles of hyalite opal covering an unknown brown/grey colored matrix, from Zacatecas, Mexico. The hyalite opal shows a bright green fluorescent response under both SW and LW UV, and also exhibits yellow/green daylight fluorescence. The green fluorescent response seen in this material is due to trace amounts of uranium included in the opal silica. Due to the uranium content, this specimen is moderately radioactive and was measured at 200-300 cpm at 1 cm. The size of this piece is 10.1 x 6.71 x 3.81 cm, and it weighs 165 grams.