96 



[Proc. B.N.F.C., 



3. Tildarg, E. of Sandy Braes (April, 1907). This Basalt 



shews Natrolite, with inclusions of Felspar and Augite. A 

 peculiar feature is the inclusion of nodules of glassy material 

 connected by shreds of same to the ground of the rock. 



4. Bruslee, near Ballyclare (March, 1908). The Natrolite here 



shows inclusions of Felspars and very large Augites ; glass 



plentiful. 



The most typical of these deposits are the specimens found at 

 Ballyhenry. The Basalt of this district is a compact, finely crystalline 

 rock composed of Plagioclase Felspar, and Augite, with a smaller 

 proportion of Olivine. It contains a good deal of fresh Magnetite, 

 which is more plentiful in some parts of the rock than others. A 

 greenish-yellow interstitial glass occurs, particularly around the 

 Zeolites. The latter, chiefly Natrolite, Analcime, and Chabazite 

 occur in cavities which are both irregular and spherical in shape. 

 Natrolite is invariably the first Zeolite deposited in these cavities, 

 following immediately upon the glassy film. In the accompanying 

 diagrams Fig. 1 (Plate IV.) represents the normal junction between 

 the Basalt and Zeolite, with the thin layer of green glassy material 

 between the two. Fig. 2 represents the abnormal junction where 

 this layer is brecciated and found coating large crystals of Felspar, 

 Augite, and Magnetite, which latter are completely enclosed by 

 the Natrolite in many cases. The following measurements shew 

 the comparative lengths of the crystals in the ground of the rock, 

 and of those in the holo-crystalline portion and inclusions. 



GROUND. HOLO-CRYST. 



Felspar 1 — '3 m.m. v to 2' m.m. 



Augite *i — '2 „ i" „ 1 "6 „ 



Magnetite -05— -3 „ -4 „ '8 „ 



The included Augites do not exhibit their crystalline outline 



but the Felspars are perfectly idiomorphic — in the Whitehead and 



Bruslee specimens however the included Augites are idiomorphic. 



A peculiar feature is the development of hollows filled with 



Natrolite within many of the included Felspars. 



