REPORT OF THE DIRECTOR 1917 I&I 



A further fact made clear by the analyses is the small amount of 

 potassium in the oolite. This is a matter of interest in its bearing 

 upon hypotheses, to be treated later, which explain the Clinton ores, 

 and others more or less similar, as resulting from the alteration of 

 glauconite. In this connection, too, it may be noted that^ while 

 the silicate of the gray oolite is ferrous, glauconite is essentially a 



ferric silicate. 



By way of comparison, analyses of other minerals are given which 

 are related to chamosite either mineralogically or in manner of 

 occurrence, as well as, possibly, of origin. Further reference will 

 be made to these in the sequel. 



A second variety of oolite, differing markedly in appearance from 

 that just described, occurs somewhat frequently in small amounts, 

 not as a separate bed, as is the case with the gray oolite, but scat- 

 tered irregularly through the ore itself, and differing from it chiefly in 

 being of a pale grayish green color instead of red (plate 4, figures 1 

 and 2). The relation of this green oolite to the ore clearly shows the 

 former to be merely a secondary modification of the latter. The 

 two varieties pass into each other by imperceptible gradations and 

 it sometimes happens that, when the ore is traversed by a joint or 

 irregular crack, the original red color has given place to green, 

 obviously as the result of the action of solutions passing through 

 the opening. Indeed, it is quite evident that this green oolite is 

 strictly analogous to the green spots and bands so commonly 

 developed in red formations by circulating solutions. 



Samples for analysis, representing the green oolite and the red ore 

 from which it is derived, were taken from a single large specimen 

 of the ore, shading gradually into the green oolite at one end. 

 The results are shown below, analysis 9 being the green oolite 



and 10 the ore. 



Recalculation of the analyses of the soluble portions, by the same 

 method that was used for the dark-gray oolite, gives, for no. 9, a 

 total of 37.23 per cent of ferrous silicate, whose composition is shown 

 in ga, and, for no. 10, a total of 22.07 per cent of ferrous silicate, 

 whose composition is shown in 10a. 



These results are less trustworthy than those derived in the pre- 

 ceding cases because of certain peculiar features of the materials 

 analysed. The green oolite, no. 9, shows a deficiency in C0 2 which 

 requires the calculation of all MgO'to the ferrous silicate while, on 

 the other hand, the red oolite, no. 10, has a large excess of C0 2 

 which uses up not only all of the MgO but, in addition, a consider- 



