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



Another interesting locality, where celestite-bearing rocks 

 may be studied to advantage, is the Woolmith quarry, located 

 in Exeter township, midway between Maybee and Scofield, 

 Monroe County, Michigan. The geology of this county has 

 been thoroughly studied by Sherzer and a detailed account of 

 the various strata occurring at the Woolmith quarry is given 

 in his excellent "Geological Report of Monroe County."* 

 Sherzer distinguishes nine different beds at this locality and 

 assigns them to the Monroe series, which is, doubtless, the 

 equivalent of the Salina in New York. For this discussion, 

 however, it is important that the strata near the surface contain 

 a very large amount of celestite disseminated throughout 

 them. In several specimens, taken from what Sherzer calls 

 bed A, crystals of celestite can be easily recognized. That 

 some substance possessing a high specific gravity is present is 

 evidenced by the fact that several determinations of the spe- 

 cific gravity of one of the specimens gave figures as high as 

 3*45. These rocks are dolomitic and therefore ought to pos- 

 sess a specific gravity of about 2*85 to 2*90. Where they have 

 been protected from the action of water, these rocks are com- 

 pact, but where they have been exposed for only a short time 

 they assume the porous structure characteristic of celestite- 

 bearing rocks. As in the other localities, referred to above, 

 many of the rocks possess cavities sufficiently well preserved 

 so that the orthorhombic outline may be readily recognized. 



In the lower beds many cavities of an irregular nature, vary- 

 ing from a few inches up to a foot or two, are found. In 

 these cavities beautiful crystallizations of celestite are to be 

 noted. In some instances, the crystals are from four to six 

 inches in length. Associated with the celestite there often- 

 times occurs a considerable quantity of native sulphur and 

 also, now and then, small amounts of calcite. The celestite is, 

 however, by far the predominant mineral. 



At this locality the changes, which are now actually taking 

 place, may be followed very easily and furnish the best of evi- 

 dence in proof of the solution of celestite in the strata near 

 the surface and deposition in the lower and cavernous beds. 

 The well-developed crystals of celestite, — in some cases 

 four to six inches in length — which are found in these 

 larger cavities in the lower strata, are therefore the result of 

 transportation by means of solution from the higher to the 

 lower layers of rock, and not, as Sherzerf suggests, due to the 

 interaction in these cavities of a solution of gypsum with 

 another containing a soluble salt of strontium. That the celes- 

 tite has actually gone into solution is shown, first, by the pecu- 



* Part I, volume viii of the Geological Survey of Michigan, 1900. 

 f Geological Report of Monroe County, 1900, 208. 



