Among Midwest mineral collectors, the Linwood mine was previously best known for its exceptional calcite and marcasite, as well as the occasional find of barite specimens, which were considered to be rare. The opposite is now true since the 2011 discovery of a large cavern lined with barite crystals, thousands of which are now finding their way into the collectors' market. This cavern arguably contains the largest single crystals of barite ever discovered in the United States and certainly some of the largest in the world. Here, we review the geology of the Linwood mine and its relationship to the mineralogy, fluorescence, phosphorescence, and origin of barite.
Jared T. Freiburg, a geologist at the Illinois State Geological Survey, is the owner of Saga Minerals, Inc., and is currently pursuing a PhD in geology from the University of Greifswald, Germany.
Dr. Julio A. N. T. Soares is a senior research analyst at the Fredrick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.
Pingfan Hu is an undergraduate student studying chemical engineering and minoring in geology at the University of Illinois at Urbana-Champaign.