1907-1908.] 95 



Analcime-Basalts, 1 as a primary rock-forming substance, but the 

 general tendency at the present day is to regard Analcirne and 

 other Zeolites as secondary decomposition products, except in 

 such particular cases where definite evidence to the contrary is 

 forthcoming. While investigating the minerals associated with 

 the Carnmoney Chalcedony in 1906 I found several specimens of 

 Zeolites showing peculiar inclusions of the mother-basalt, con- 

 sisting of grains of Magnetite in one case and long thin filamentous 

 shreds of Basalt in another. These specimens in themselves were 

 convincing evidence in favour of a theory, accounting for the 

 origin of Zeolites and other " secondary " minerals in lavas 

 as primary formations of almost contemporaneous age with the 

 primary rock-forming minerals. This view I have held since 1900, 

 and formulated it, provisionally, into a definite working theory in 

 1906, which was developed still further last year. 2 Since then 

 abundant evidence has turned up as the result of a careful and 

 extensive examination of the junction between Zeolite and Basalt 

 at many localities in Co. Antrim. The following localities, with 

 one exception, were discovered by the writer of this paper, and in 

 each case Natrolite is the Zeolite found to contain inclusions of 

 primary minerals : — 



1. Ballyhenry, near Carnmoney (May, 1906). The Natrolite 

 at this place contains inclusions of Felspar, Augite, and 

 Magnetite. 



2. Whitehead, Island Magee (April, 1907 • found by Mr. 



Andrew Duncan, B.Sc.j. This rock shews drusy cavities 

 containing Natrolite, with inclusions of Felspar and Augite ; 

 glass very sparse. 



1. For references to literature on the subject of Analcime-bearing lavas 

 vide Harker's "Petrology" pp. 139-140, 149-150, text and footnotes. 1902. 



2. Vide the author's Papers on "The Origin of the Carnmoney Chalce- 

 dony," and "The Geogony of Some Secondary Minerals ;" Proc. B. N. F. C. 

 vol. V., series II., p. 420^. set/., and pp. 501-2. 1906-07. 



