Located adjacent to 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 crystals. Less known is that the Linwood Mine also produces the largest euhedral barite crystals in the United States. Some of the Linwood barites show a very interesting fluorescent/phosphorescent response under UV.
This is a specimen of light golden/smoky colored barite crystals on a siltstone matrix. The largest crystal measures 7.9 x 3.1 cm, and is double terminated. These crystals are exceptionally transparent and well-formed. The barite shows a ghostly blue/white fluorescent response with greenish phosphorescence under short wave and mid wave UV, but is only dimly fluorescent under long wave. This specimen measures 13.8 x 9.2 x 5.9 cm, and weighs 517 grams.
Some of these photographs were featured in the article "Barite from the Linwood Mine," written by Jared Freiburg, et al., published in the Jan/Feb, 2017, issue of Rocks & Minerals.