THE DECCAN TRAPS 771 



tered and the small augite anhedra are not as strictly intersertal, so that 

 the fabric is more nearly a common basaltic one. The augite grains are 

 pale brown, like that in the coarser types, but of a lighter shade. The 

 specimen from Ketool Hill, Cutch, contains some small subhedral crys- 

 tals of olivine, and this specimen differs from the others also in that much 

 of the feldspar is in equant, rather than in tabular, crystals. Small 

 grains of magnetite, many of them sharply euhedral, are rather abun- 

 dant, the specimen from Belgaum showing this mineral (or ilmenite) 

 also in thin tables. 



(d) Fine grained, liyalitic. — Specimens of this type come from the 

 following localities: Jiran, near Neemuch* (28/556) and Jerkhera, 

 Bhopal (19/238), Central India; Bombay" (1/503) ; Junapani, His- 

 hangabad (29/567), Central Provinces; and Eamchanderpur, Eajmahal* 

 Hills 7 (28/701), Bengal. 



These specimens are all densely aphanitic and compact, mostly with a 

 dull luster, but that from Bombay shows something of the subresinous 

 luster of tachylyte. They all show a good conchoidal fracture. The color 

 is a deep, pure black, with no tinge of green or brown; no phenocrysts 

 are visible. The texture seen in thin section is a typically basaltic one — 

 very small and sharp, rectangular, relatively thick laths of labradorite 

 and small, equant but rounded grains of slightly brownish augite are 

 irregularly intermingled, with only slight simulation of ophitic fabric 

 and not showing flow texture. Throughout are small, irregular patches 

 of an opaque black substance which the higher powers resolve into a 

 colorless glass densely crowded with black dustlike grains of such small 

 size as to be resolvable with difficulty. In one or two specimens, espe- 

 cially that from the Eajmahal Hills, there are incipient crystallizations 

 of magnetite in lines of minute octahedra branching at right angles. 

 Apart from these and the black grains, which are presumably magnetite, 

 neither magnetite nor ilmenite is present. Olivine seems to be quite 

 absent from these rocks. 



Before passing on to the chemical composition of these basalts, a few 

 words may be given to a somewhat striking modal feature. It is clear, 

 from the typically ophitic texture of the more coarsely grained specimens, 

 as well as from the euhedral character of the feldspars and the anhedra 1 

 forms of the augites in the last type, that the labradorite was the first 

 mineral to crystallize, or at least that it began to crystallize before the 

 augite. This is but another example of a feature that is commonly ob- 



7 The basalt flows of the Rajmahal Hills belong to the Upper Gondwana and do not 

 properly form part of the Deccan traps. See Wadia : Geology of India, 1919, pp. 129, 

 258 ; Reed : The Geology of the British Empire, 1921, p. 283. 



