42 FLUORSPAR DEPOSITS OF SOUTHERN ILLINOIS, [bill. 255. 



and where both are sandstones, as at the McClelhm and pro])ahly tlie 

 Daisy. Since the faulting is deep enough to cut a considerable suc- 

 cession of sandstones and limestones, it is obvious that if the ores con- 

 tinue to any depth the relations at the surface may change, even to the 

 point of reversal. In such a region as this it is also true that the fault 

 planes which bring limestone into contact with sandstone are most 

 easily recognized, and hence are the ones first prospected. Tender the 

 circumstances the seeming close relation of the ores watli the Ste. 

 Genevieve limestone may be deceptive, though in the absence of deep 

 mining judgment on the point must be susj^ended. 



Rehdions to topography and ini(/ei'(//'oini<I water level. — The ore 

 bodies do not seem to bear any close relation to topography. The\' 

 are found on the upland, as at the P]mpire; in hillsides, as at tlie Lead 

 Hill mine, and under bottom land, as at the Rosiclare. In general 

 tliey are on the slope, since there is very little level ground in the dis- 

 trict. There is not, however, that close relation to topograjjhy which, 

 for example, is characteristic of the ore bodies of the Lake Superior 

 iron ranges." 



The relations to underground water level appear to be equally 

 fortuitous. In general, the mines are relatively dry and the small 

 amount of water handled seems to be entirely of local origin. At 

 the Hosiclare mine it is clearly oxidizing and varies with local rain- 

 fall. As this is the deepest mine, it would presumably have tapped 

 an}^ deep waters wdiich might occur in the veins, and yet the total 

 amount of w^ater pumped under ordinary conditions is very small, 

 being estimated at 75 gallons ])er minute. In general, the mines, 

 where of any depth at all, are below^ the local level of underground 

 water. 



AUe7'atio)i of ores. — The ores are very little altered. Beyond the 

 occasional occurrence of small bodies of zinc carbonate near the sur- 

 face, there are none of the usual signs of decay and alteration com- 

 mon to sulphide ores. Even where oxidation has been carried to some 

 depth, as at the Hubbard and Cook mines, it has not much aft'ected 

 the vein matter, but has proceeded rather along cross fractures or 

 through the country rock. In the long period of erosion in which 

 the upper i)ortion of these veins Avas cut off, very little material was 

 carried down into the vein. That which was eroded seems to have 

 been mechanically broken off or to have been dissolved and carried 

 away wnthout local reconcentration. In the presence of the more 

 easily soluble limestone, surface Avaters do not attack with any vigor 

 the fluorite or the minerals confined Avithin it, and so the vein mate- 

 rial as now exposed is practically unaltered. The bodies of zinc car- 

 bonate occasionally found mark local and exceptional reconcentrations. 



« Van Uise, C. R., Twenty-first Ann. Kept. U. S. Geol. Survey, pt. 3, 1901, pp. 329-330. 



