l86 NEW YORK STATE MUSEUM 



As already indicated, the spherules of the oolite are of simple 

 composition, consisting of the silicate, alone, surrounding cores, 

 usually, of rounded quartz. Obviously, this silicate must either be 

 primary or derived from the alteration of an earlier mineral, 

 presumably oxide or carbonate. As to the latter compound, though 

 present in the - cement, no evidence has been found that it has played 

 an important role in the formation of any of the oolites, either gray 

 or red, similar to that which Cayeux assigns to it in the French 

 ores. 



The case of hematite is, of course, entirely different, this mineral 

 being the chief constituent of the spherules in the red oolite, or ore, 

 and appearing in small amount in the gray oolite, though in the 

 cement rather than the spherules. 



That, under certain conditions, the silicate might be derived 

 from the oxide, there can be no doubt but on geological grounds 

 such derivation can not be accepted in the present case. The 

 association of the gray oolite and the ore is such as to show that 

 both have been subjected to essentially identical conditions since 

 their formation. The gray oolite, unlike the green variety in the 

 ore, is a definite layer and no reason appears why, if deposited as 

 oxide, it should have been altered to silicate any more than the 

 ore less than 2 feet above it. Moreover, it is difficult to see how 

 the small amount of hematite in the cement of the gray oolite could 

 escape alteration which was so markedly changing the spherules. 



These spherules, furthermore, differ in detail from those of the 

 ore, being often less nearly spherical, showing evidence of distortion 

 while soft and, frequently, blending one with another, so far -as 

 theij outer layers are concerned (plates 1, 2 and 3). These are 

 doubtless somewhat accidental distinctions, but they are thought 

 to have some significance. 



The total impression made upon one who has studied the gray 

 oolite in the field and laboratory is that the ferrous silicate is distinctly 

 primary and that the absence of hematite is due to some slight 

 variation from the ordinary ore-forming conditions, rather than to 

 its secondary conversion into silicate. 



The green oolite, resulting from alteration of the red ore, is 

 evidently analogous to the green streaks and blotches of red shales 

 and sandstones. From this it might be concluded that the green 

 silicate is secondary, resulting from the alteration of the red oxide. 

 But, while this may be true in part, another explanation is possible. 



The analyses show that the ore contains practically the same 



