Heviews — Geological Survey — Geology of India. 179 



for 250 miles the northern portion of the Eastern Ghauts. To use 

 the author's words, "this giant eruptive is overlaid in part by 

 metamorphosed sediments, principally khondalite, and to a less extent 

 by laterite." 



In describing the typical light- coloured nepheline rock, greenish- 

 brown hornblende, brown biotite and magnetite grains, more or less 

 idiomorphic, occupy only a very small portion of the rock-mass. 

 Anhedra of nepheline and large irregularly rounded grains of felspar 

 constitute the major portion, the amount of nepheline being estimated 

 at 37 per cent. The most interesting constituent, as seen under the 

 microscope, is the felspar, which is really a complex of the ordinary 

 perlitic type; a small quantity, equal to about one per cent., of 

 original calcite also occurs. The bulk analysis of the rock shows 

 52 per cent, of silica, 26 per cent, of alumina, 3 per cent, of iron- 

 oxides arid magnesia, nearly 2 per cent, of lime, and 14 per cent, of 

 soda and potash in equal amounts. An analysis of miaskite from the 

 Urals is given for comparison. The Director remarks that, judging 

 by the previously known associations of this class of rock in South 

 India, Ontario, and Montana, we should be justified in searching for 

 corundum deposits. 



There is a further report on the manganese-bearing rocks. The 

 typical rock of this series (intrusive) is composed of potash-felspar, 

 manganese- garnet, and apatite. Its common form when fresh has 

 a texture resembling a medium - grained granite. Mr. Termor 

 proposes to distinguish this kind of rock as hodurite, after the Kodur 

 manganese mine, where it is well exposed. It is further suggested 

 that, as the manganese-garnet is intermediate in composition between 

 spessartite (manganese alumina-garnet) and andradite (lime iron- 

 garnet), the term spessart-andradite might be used, and shortened for 

 convenience into spandite. Thus we have a newly-named rock with 

 a newly-named mineral to match. 



Economic Geology. 



The following remarks are based partly on Mr. Latouche's state- 

 ment for 1905, and partly on Mr. Holland's Report for 1906. 



In the Geological Magazine for July, 1907, we noticed some facts 

 in connection with the " Mines and Minerals of the Indian Empire," 

 based to a cei'tain extent on Mr. Holland's Report for 1903. It can 

 scarcely be expected that any great change has taken place in two 

 years, i.e. from 1903 to 1905. Yet there is an increase in the total 

 value from £4,988,527 in 1903 to £5,707,956 in 1905, and the 

 increase has been steady ever since the beginning of the present 

 century. Gold still heads the list, being nearly double the value of 

 the coal. The greatest leap, however, has been made in petroleum, 

 which has risen from . £354,365 in 1903 to £604,203 in 1905— 

 doubtless due to exploitation in Burma ; whilst the yield of rubies in 

 that country has fallen from £98,575 to £88,340 within the period. 

 Amongst the various mineral products dealt with the following may 

 be selected for brief notice. 



Bauxite. — The more aluminous laterites of India yield in abundance 

 samples which contain nearly 60 per cent, of alumina, with less 



