smith] LEAD, ZINC, AND FLUORSPAR OF WESTERN KENTUCKY. 2.11 
occur along the fault or in a fissure not far from and parallel to the 
fault. Veins have been occasionally noted in groups of two or more, 
either parallel or arranged en echelon. Their width is variable; the 
maximum thus far recorded — in the case of well-defined veins — is 
nearly 15 feet. Most of the important veins, however, do not exceed 
6 or 8 feet in width. The veins all dip at a high angle. 
Most of the veins show distinct evidence of movement either in the 
displacement of the beds on the opposite sides of the fissure or in 
shearing with or without well-defined slickensiding. The shearing 
occurs both in the vein itself — especially near the walls — and in the 
country rock, where it may extend as much as 50 feet from the veins. 
The walls of the veins are usually, though not always, well defined, 
and are frequently marked by pronounced slickensiding. One or 
both walls are often fractured where the vein is in limestone, and are 
frequently much seamed with minute veins of calcite or fluorite. 
This seaming also frequently accompanies ordinary fracturing of the 
limestone where no vein has been formed. The shear planes are some- 
times marked by thin, clayey partings, especially in the Chester sand- 
stone. Also, where the veins are adjacent to this formation, dragged-in 
shales along the walls are not uncommon. These sandstones, where 
intersected by fissures, whether the latter are filled with vein matter 
or not, or where they have been filled with igneous rock, have been 
as a rule silicified, to a greater or less extent, to a hard quartzite. 
This quartzite, being resistant to erosion, appears in dike-like forms 
above the surrounding rocks, the shearing giving the effect of verti- 
cal or highty inclined bedding. 
The principal minerals of the district are galena and its oxidation 
products; sphalerite ("blende") and its oxidation products, smithson- 
ite (" carbonate"), and hydrozincite; pyrite (or marcasite), greenock- 
ite, fluorite ("fluorspar"), barite, calcite ("calc spar"), quartz, and 
ankerite. Nearly all of these occur either in the veins or in connec- 
tion with them. In addition, bitumen is occasionally found in the 
veins. 
Fluorite. — Fluorite is by far the most important of the vein min- 
erals, comixhsing, as a rule, the greater part of the vein, the remainder 
being made up of a varying proportion of other minerals, with 
dragged-in country rock. In some cases the vein is composed almost 
wholly of fluorite ; in others the proportion of other substances is so 
large as to make it unprofitable to work the deposit. The associated 
minerals and rock fragments may be found throughout the vein, but 
in general they are mo^t abundant toward the margins. The fluorite 
veins frequently show a pronounced banding, due either to shearing 
or to a variation in the grain of the fluorite in bands parallel to the 
walls of the fissure. 
In the Chester sandstone fracturing has frequentty resulted in 
brecciation rather than in a well-defined fissure, and the breccia may 
be more or less completely cemented with fluorite. Barite may occur 
