318 Scientific Intelligence. 



In addition some gneisses and other rocks are described. Among 

 them is a syenite and syenite porphyry which are shown to have 

 anorthoclase (soda microcline) as the feldspar, and the author 

 believes this to be a sufficient ground for the erection of a new 

 rock group and proposes the names of hatherlite and pilandite for 

 them respectively. Probably the majority of petrographers will 

 hardly agree to this, since as commonly understood the syenite 

 family is one composed essentially of alkaline feldspars in general 

 and not one particular variety of them. As a matter of fact, the 

 pure potash feldspar is of very rare occurrence as a rock-ingre- 

 dient and the great majority of the so-called orthoclases contain 

 the albite molecule to a greater or less extent. Moreover since 

 the analyses of the feldspars of the rocks mentioned show that 

 they contain a very considerable quantity of lime, it appears ques- 

 tionable whether they should not be classed as abnormal oligo- 

 clases rather than anorthoclase (soda microcline) ; they are clearly 

 not typical examples of the latter. 



Very full and painstaking investigations have been made in 

 this work of the augitic constituents of the rocks mentioned 

 which have been separated and analyzed, but it seems rather 

 curious from modern standpoints that with so much chemical 

 investigation of the constituents no mass analyses of the rocks 

 except in one case have been made. This is a rock consisting of 

 enstatite crystals including 4*5 per cent of anorthite plates. The 

 analysis gave : 



Si0 2 Ti0 2 A1 2 3 Fe 2 3 FeO MgO CaO H 2 Sp. G.=33 



5523 0-14 2-08 394 625 29'29 T68 112 = 100*03 



It is an enstatite pyroxenite from the Central Marico District. 



l. v. P. 



10. On the Occurrence of Corundum. — Two recent papers on 

 the occurrence of corundum in widely separated parts of the 

 world deserve to be mentioned. One of these, by T. H. Holland,* 

 discusses in detail the various corundum localities, including the 

 gem varieties, ruby and sapphire, in India and the adjacent 

 countries. The second paper, by W. G. Miller,! describes the 

 corundum and associated minerals of Eastern Ontario. 



The most interesting point brought out in both papers is the 

 fact that corundum occurs so often associated with igneous rocks ; 

 this fact has also been recently established in other regions. Mr. 

 Holland accepts the fact that in certain cases it may have a sec- 

 ondary origin, as shown by Professor Judd for the ruby, but for 

 the most part he regards it as an original constituent, though 

 often due to the local excess of alumina. The Indian localities 

 are divided into those in which the corundum occurs with basic 

 rocks and these in which its associates are siliceous, that is, acid. 

 In the former class pyroxene is the predominating constituent, 



* A Manual of the Geology of India : Economic Geology by the late Professor 

 V. Ball. Second edition revised in parts. Part I, Corundum, by T. H. Holland • 

 pp. 79, Calcutta, 1898. 



f Report of the Bureau of Mines, vol. vii, third part, pp. 207-265, Toronto, 1898. 





