Washington — Charnockite Series of Igneous Rocks. 333 



Or 0-56 



Ab -. 4-19 



An 12-23 



Di 18-97 



Hy 42-35 



01 13-01 



Mt 4-41 



II 2-43 



Ap 0-67 



This gives the rock the symbol IYMV2.1.2, that is in the 

 subrang named hilose by Daly. The rock from JBahia falls in 

 the same position, while the other two, C and E, with the sym- 

 bol IY.l. 2.2.2, fall in a subrang which has been called pali- 

 sadose by J. Y. Lewis (1908) and hudsonose by Rogers (1911). 



The name bahiaite from an occurrence in Brazil was recently 

 suggested* for the phanerites composed essentially of hyper- 

 sthene and hornblende, the name being of equal nomenclatorial 

 rank with wehrlite, Iherzolite, saxonite or cortlandtite. The 

 rock has been noted by Rogers in the Cortlandt Series, by 

 Merrill in Montana and as India furnishes another locality, 

 whose rock closely resembles the type, the motex (combination 

 of mode and texture), is seen to be very widespread, and the 

 application of the name would seem to be justified. 



General Characters. 



The general characters — modal and chemical — of the Indian 

 Charnockite series may be summed up as follows : 



The rocks range from highly quartzose hypersthene granite 

 (charnockite), through hypersthene-quartz diorites (and pos- 

 sibly monzonites), norites and other intermediate rocks to 

 hornblende hypersthenite. 



Except in the granite little or no microcline is present, the 

 dominant feldspar in the intermediate types ranging from 

 Ab 3 An x to AbjAUj. A very striking peculiarity of these soda- 

 lime feldspars is the tendency to absence of the usual twinning 

 lamellae, so that they simulate orthoclase. The characteristic 

 and constant mafic mineral is hypersthene, which is high in FeO, 

 and with a constant peculiar pleochroism : c bluish gray, a and b 

 pink. This hypersthene is also characterized by the prevalence 

 of the cleavage or parting parallel to 5(010), and the general 

 absence of the usual prismatic cleavage, so that many sections 

 show apparent oblique extinction. Augite, when present, is 

 only in very subordinate amonnt and is apt to show a faint 

 pleochroism like that of the hypersthene. Hornblende (like 

 augite) occurs only in the more mafic members, but offers no 

 *H. S. Washington, this Journal, xxxviii, p. 86, 1914. 



