Shale and fluorite matrix is the base for prismatic, transparent calcite crystals with a smoky tinge from hydrocarbon inclusions. True prismatic calcite is rare from southern Illinois. Very fine locality specimen as well as a fine calcite miniature. Collected from old underground workings c. early 1960s. Doubly terminated crystals to 1.2 cm. Excellent condition. Dr. Perry & Anne Bynum Collection. (Entered into Ross Lillie database as RCL2494).