Rosiclare Subdistrict

By far, the richest vein subdistrict in the IKFD is the Rosiclare Subdistrict. The Rosiclare Subdistrict is located in Hardin County, in southeastern Illinois, and extends from the Ohio River northward through the village of Rosiclare to just north of Illinois Route 146. The Rosiclare Mine, which operated for more than a century, was at one time the largest fluorspar mine in the United States and possibly the world. Several adjacent mines, notably the Argo, Blue Diggings, Daisy, Eureka, and Hillside, were also major producers. The veins are aligned along a set of north-trending normal faults of slight to moderate displacement (Figure 6). Mineralization is predominantly fluorite, along with calcite and lesser amounts of quartz, galena, and sphalerite. Barite in the Rosiclare Subdistrict is not common, in contrast to some other parts of the IKFD. The widest veins in the Rosiclare Subdistrict typically lay where one or both walls of the fault were composed of limestone or highly calcareous units. Fluorspar also replaced an earlier-phase calcite already present within the faults and fractures. Both the fault and vein were usually named the same; thus, the Rosiclare Vein lay along the Rosiclare Fault. From east to west, the major veins are named the Hillside, Rosiclare, Daisy, Blue Diggings, Argo, and Knight. The biggest problem in the Rosiclare Subdistrict was flooding, which forced a number of mines (including the Rosiclare) to shut down temporarily or permanently. In mines at the southern end of this subdistrict, fissures may have channeled water directly from the Ohio River into underground workings.

The veins in the Rosiclare Subdistrict were developed along an intricate system of faults that bound the southeast side of the Rock Creek Graben. Specifically, veins of unusual width and richness coincide with an approximately 3-mile segment of the fault zone where the strike changes from its usual N40°–50°E to N0°–20°E. We are not aware of any authors who have addressed the structural implications of this bend in the fault system, but correlation of the rich mineralization with the bend is inescapable. We speculate that the Rosiclare Subdistrict represents a discrete area of transtensional or pull-apart action along a system that probably had a small strike-slip component. The nearly vertical attitude of the richest vein, the Rosiclare Vein, is suggestive of strike-slip. Transtensional, pull-apart grabens have been documented along elements of the Fluorspar Area Fault Complex in far southern Illinois. This style of deformation creates large, open fissures that facilitate the movement of ore-bearing fluids. The propensity for flooding and the occurrence of mud pockets at considerable depth also imply wide-open fissures along the veins.

Some faults bifurcate, split, or merge with other faults; thus, tracing the individual faults becomes difficult. The mining companies generally chose the names of the faults and mines, sometimes after property owners or mine operators. Changing ownership and different companies mining extensions of the same vein further complicated the names applied to the veins and faults. Near the southern end of the Hillside Mine, the Hillside Fault splits into two main segments. The easternmost extension is named the Hillside, but the western segment is called the Rosiclare Fault. The Rosiclare Lead and Fluorspar Company controlled production on the northern end of the Rosiclare Vein, whereas the Fairview Fluorspar and Lead Company, Franklin Fluorspar Company, and Aluminum Ore Company controlled the southern portion of the Rosiclare Vein. Some historical documents refer to the southern portion of the Rosiclare Vein as the Rosiclare-Fairview Vein. This is confusing because a Fairview Shaft is located west of the Rosiclare Vein, along the southern extension of the Blue Diggings Vein. The Hillside Fluorspar Mines were sold to the Inland Steel Company in June of 1945. The Mahoning Mining Company was renamed the Ozark-Mahoning Company, Mahoning Mining Division in December of 1946, and the Aluminum Ore Company was renamed the ALCOA Mining Company in 1948. The extension of the Rosiclare Vein to the south in places has been called the Rosiclare, Fairview, Good Hope, Extension, and Annex Vein. The extension of the Daisy Vein southward has been called the Blue Diggings. The ore bodies along the Rosiclare Vein were more persistent in width and length, whereas the widths of the Daisy and Blue Diggings Veins were erratic. The average width of the economic veins varied considerably, but mined thicknesses ranged from a few feet to 40 feet wide .

A few mines operating in the Rosiclare District were described in pre-1900 newspapers and journals, but the precise locations of most of these mines were not certain. William Pell was reported to have mined fluorspar along a vein near the Rosiclare Mine in 1842. The Pell operations seem to have been followed by Mullins and Argyle. The Pell Fluorspar and Lead Company was actively operating along a vein 10 to 30 feet wide in 1889. In 1889 and 1890, the Mullins Fluorspar and Lead Company was installing a concentrating plant for the recovery of lead and fluorspar, reorganizing mining, and constructing a mile-long tramway to connect the mines and mill. Other pre-1900 documents indicate that the Illinois Lead and Fluorspar Company may have succeeded the Mullins Fluorspar and Lead Company. In 1894, the Argyle Mine was reported to be operating and installing new equipment. The individual mines within the Rosiclare District are discussed below in a general north-to-south order.