526 TIIK GEOLOGY OF NEWBRIDGE, NEAR BATHURJST, N.S.W., 



Microscopically, it is seen that the rock was originally made up 

 of augite and felspar phenocrysts, with subordinate ilmenite, set 

 in a felspathic ground-mass. Subsequent alteration has changed 

 all the ilmenite into leucoxene, and the felspathic base has become 

 partly epidote and sericite. The phenocrysts of felspar are still 

 determinable by their extinction angles, and are andesine. The 

 augites are beginning to be converted into epidote and chlorite, 

 the action commencing at the border, and leaving the centre of 

 the crystals unaltered. They are frequently twinned parallel to 

 010, and occasionally diagonally. Radiate aggregates of chlorites 

 in green and brown spherulites also occur. There are a few 

 crystals of pyrites, but iron ores are vei-y subordinate. A micro- 

 photograph of this rock is shown on Plate xxiii., fig. 1. 



The andesites developed here are a portion of a large area of 

 intermediate rocks, which runs west to Blayney. In it several 

 important mines are situated, notably those of Cadia. Two rock 

 descriptions by Mr. Card* show the similarity of rocks of this 

 district with those of Newbridge. 



(a) Annadale Copper Mine, Blayney. — "These are augite- 

 andesites in diflerent stages of alteration, the alteration taking 

 the form of a development of epidote and to some extent chlorite." 

 (6) Mt. Sugarloaf. — "These are andesites, showing a development 

 of epidote, and containing hornblende. I am of the opinion that 

 the hornblende is very probably of secondary origin, resulting 

 from the paramorphic change of the augite. The augite in the 

 specimen is distinctly uralitic." 



The andesites of the Canoblas are not a portion of this area, 

 but are of a much later age. 



In the south-western portion of the Parish, and in or near 

 Portion 17, there is an occurrence of asbestos. It is in veins 

 about half an inch wide, running through decomposed andesite. 

 The fibres are short, rarely three inches long, and rather brittle. 

 The asbestos is quite anhydrous, and has the optical properties of 

 tremolite. It is probable that it has been formed from the augite 

 of the andesite by uralitisation and solution. 



* Rec. Geol. Survey N. S. Wales, iv., p. 159. 



