E. H. Kraus — Celestite- Bearing Rocks. 287 



the mineral. The celestite, however, which has been studied 

 up to the present time has, in so far as my knowledge goes, all 

 been of secondary origin, in that it has always been found in 

 the cracks, crevices, or cavities in the rocks. 



The discovery of the " Strontium " or " Crystal " cave in 

 1897 showed conclusively that there must have existed some- 

 where on the island a very large amount of celestite. This 

 cave is perhaps 25 to 30 feet in its extreme dimensions. The 

 form is somewhat irregular and the interior is lined on all sides 

 with well-developed crystals of celestite, some of which are 

 eighteen inches in length. In opening this cave to the public 

 it was necessary to remove some of these crystals in order that 

 suitable passageways might be made. The owner, Mr. G-us- 

 tave Heinemann, estimates that in so doing no less than 150 

 tons of celestite were removed. This, however, represents but 

 a small portion of what still remains. 



G. F. Wright,* in describing this cave, speaks of it as an 

 immense geode. There is no doubt, whatever, of the second- 

 ary origin of the celestite. An examination of the rocks im- 

 mediately overlying the cave shows that they are of a more or 

 less porous nature. 



At the time of my visit to the island in August, 1904, several 

 wells had just been drilled — one on the farm of Louis Schiele 

 on the southeast shore of the lake, and the other at the hotel 

 of August Markley on the road extending southward from the 

 main dock. This last well is not over a quarter of a mile 

 from the " Strontium" cave. Many cores were obtained from 

 these wells. These cores show that the rocks near the surface 

 are very porous. In many instances the cavities are well pre- 

 served and reveal the celestite outline. The rocks near the 

 surface show small cavities, but as we go deeper the cavities 

 become much larger, some over an inch in diameter, and the 

 rocks are crossed by numerous cracks. It is in these larger 

 cavities and cracks that excellent crystallizations of celestite 

 are found. These lower cavities, however, do not possess a 

 definite outline, but are more or less irregular. The crystals 

 do not in all cases completely iill the cavity, and in no case 

 does the cavity conform to the celestite outline, as is the case 

 when the mineral occurs disseminated. Figure 1 shows a core 

 from the Schiele well. This core is from the strata near the 

 surface, and shows clearly the porous condition of the rocks. 

 It is not possible for me to give exact figures as to the depth at 

 which this core was obtained, nor can I state how far below 

 the surface celestite is first encountered filling the larger cavi- 

 ties and cracks, for no detailed record of either this or the 

 * Science, viii, 502, 1898. 



