792 WHITMAN CROSS 



and basic kodurites, to manganese-pyroxenites containing rhodonite 

 and other manganese pyroxenes."^ The kodurite proper is a rock 

 now much decomposed, but assumed to have consisted of ortho- 

 clase, a manganiferous garnet, and apatite. Opal now takes the 

 place of the supposed orthoclase. 



What are considered to be difficulties in the way of classify- 

 ing the kodurite and other highly manganiferous rocks in the 

 Quantitative System lead Fermor to conclude that it fails in several 

 respects when apphed to such rocks or to possible ones rich in nickel, 

 barium, strontium, or lime. On the other hand, it is said that 

 classification of the kodurite and other rare rocks by Hatch's 

 system is eminently satisfactory. 



The evident fairness with which Fermor has essayed the classi- 

 fication of the kodurite rocks in the Quantitative System relieves 

 his discussion, in most respects, from the charge of controversial 

 tone, notwithstanding his very evident prejudice against some 

 features of that system. The problems presented by such rocks 

 are real ones and must be solved if manganese-rich igneous rocks 

 occur, but there is a point of view from which the result reached 

 by Fermor is very much more satisfactory than it seems to him, as 

 will appear in the following discussion. 



THE CHARACTER OF THE KODURITE SERIES 



The rocks of the Kodurite Series were specially described by 

 Fermor^ some years ago. They occur in the Archean Complex 

 of the coastal plain belt of the Madras Presidency about midway 

 between Madras and Calcutta. In view of the importance of this 

 series, if of igneous character, it is necessary to point out at once 

 that this character is by no means self-evident, and that much 

 further proof than that offered by Fermor is necessary before 

 geologists unfamiliar with the occurrence can be expected to accept 

 the view of their igneous origin. 



The kodurite rocks occur in a lowland zone of poor exposures, 

 the best being in the manganese mines where the secondary oxi- 



' L. Leigh Fermor, op. cit., p. 208. 



^L. Leigh Fermor, "On the Manganese Deposits of India," Memoirs, Geol. Sur- 

 vey of India, XXXVII, Pt. 2 (1909), "Geology," 243-79, Calcutta. 



