OL'^ 



THE GEOLOGY OF NEWBRIDGE, NEAR BATHURST, N.S.W., 



of several other veins so traced.* It is noticeable in the railway 

 cuttings that generally tlie granite veins follow the cleavage of 

 the slate, and have straight and parallel bounding walls of slate. 

 But this rule is by no means universal, for many irregular intru- 

 sions are to be seen, and even horizontal veins occur. We may 

 divide the veins into three classes, (a) granitic, (b) granophyric, 

 and (c) aplitic. 



(a) Granitic Veins. — These are the most abundant of the veins 

 that cross the railway cuttings. Man}- of them are very highly 

 decomposed. Some are only partly decomposed, and may still 

 be examined microscopically. Such an one occurs at the 1621- 

 mile peg on the new line. 

 It intrudes the slate very 

 strongl}^ as may be seen 

 from fig. 2, which is from 

 a sketch taken in the old 

 railwa}' cutting near by. 

 In Plate xxiii., fig 3, a 

 microphotograph of the 

 junction of the mica 

 schist with the granite is 

 shown. Microscopically 

 I _ //// ijjj^ -[- I the granite is seen to be 



r 1 Foot. ' ^ Jlllllll i_ -I composed of predominate 



orthoclase, with oligo- 



clase, quartz, biotite, 



muscovite, and apatite. 



Ill the Railway reserve and near to the bound arj' fence of 



Portion 65, Parish of Galbraith, there is a large vein of a beautiful, 



fresh hornblende-granite. Its exact description is : — 



Macroscopical. — Medium-sized grain (1 mm.) showing quartz 

 and felspar, with abundant short prisms of hornblende, some 

 biotite, and occasional!}^ pyrites. 



Fig. 2. — Intrusion of mica schist by granite 

 Sketch in the railway cutting. 



* These Proceedings, 1891, (2) vii. 



