28 



SEVENTH REPORT. 



The analysis of the rock from Bed A, however, shows clearly that if the sulphides of 

 iron are present in the uppermost layers, they must be present in amounts which are 

 almost insignificant when compared with that of the celestite. It is also of vast im- 

 portance to call attention to the fact that, when the rocks of the various layers in this 

 quarry are treated with dilute acid, or even boiled with water, hydrogen sulphide is lib- 

 erated. To be sure, in some instances the amount is very small but, nevertheless, even a 

 trace is of great import, indicating that a soluble sulphide, no doubt, strontium sulphide, 

 is present. We must, therefore, consider the theory that the decomposition of pj^rite 

 or marcasite by the formation and subsequent oxidation of hydrogen sulphide has given 

 rise to the native sulphur at this quarry as untenable. 



'However, when we consider, first, that the uppermost strata contain about 14 per cent 

 of strontium sulphate, which is quite soluble in water and hence easily transpoited to the 

 lower layers by the descending waters, and second, that these and the lower strata con- 

 tain considerable organic matter, and third, that there is only a negligil)le amount of iron 

 present, and fourth, that hydrogen sulphide is liberated when the rock is treated with 

 acid, it seems evident that the celestite, present in a disseminated condition and which has 

 by the action of the organic matter become partially reduced to the sulphide, must be con- 

 sidered as the source of the hydrogen sulphide. 



Hence, if the foregoing statements be true, an analysis of the rock from the more porous 

 and cavernous layers, the cavities of which contain celestite and sulphur, ought to show 

 not only the presence of strontium as a sulphate but also as a sulphide, which would be 

 indicated in the analysis as sulphur trioxide and hydrogen sul^shide, respectively. 



The following analysis w'as also made by W. F. Hunt. 



The sulphur trioxide represents the total amount of sulphur. The hj'drcgen sulphide 

 was determined directly by liberation with hydrochloric acid, absorbed in potassium 

 hydroxide, acidified and titrated with N-lOO iodine. 



The silica is present, no doubt, as free silica. The A^alue of the molecular ratios of the 

 oxides of calcium and magnesium, as also that of the carbon dioxide, give rise to the follow- 

 ing proportion : 



!SS)(:3795]: CO, (.7259) =1.004:1. 



Hence, this rock may be considered a siliceous dolomite. The sulphur trioxide ard hydro- 

 gen sulphide indicate that the strontium is present both as the sulphate and sulphide. 

 In this connection, w'e note that if the hydrcgen sulphide be considerfd as having been 

 derived from strontium sulphide, and further, if that amount of strontium, which is neces- 

 sary to unite with the sulphur^ — equivalent of 0.02 per cent hdyrogen sulphide"— to foim 

 strontium sidphide, be deducted from the value of strontium oxide, given in the analysis 

 the following relationship between the molecular ratios of the strontium oxide and sulphur, 

 trioxide, actually present, is revealed. 



\ SrO 



1. 



/ BaO • (-0061741) : SO 3 (.005616) = 1.099 



These values are so close that we must consider this evidence in support of the above 

 theory as very conclusive, namely, that the celestite, as a source of the sulphur, is parti- 



iBy difference. 



^Determinations from other portions of this same la.yer showed as much as 0. 12 per cent hydrogen 

 sulphide. The analysis was, however, not complete and, hence, is not given. 



