452 PETROLOGICAL NOTES ON N. S. WALES ROCKS, 



like that of some traclij'tes, and augite occurs in broad spongy 

 plates of considerable size. 



Finally, there is one instance of the partial recrystallation of 

 an orthoclase-grain in the gneiss to a variolitic mass of felspar- 

 laths. This change occurs at isolated spots in our rock, but among 

 the inclusions of granite in the basalts of the Auvergne, Prof. 

 Lacroix* has found a rock in which the felspar is entirely changed 

 in this manner. 



Some features recall the observations of Heineck on the melting 

 down and mingling of granite with basalt-lava in Bohemia, but the 

 process in our rocks is not nearly so far advanced as in the 

 Bohemian f. 



iii. Granitic Inclusions in the Volcanic J^ecks of Dundas and 

 No7'tons Basin. 



In my account of the inclusions in the volcanic neck at Dundas, 

 there is no mention of granite. Shortly before the quarrying 

 operations ceased there, Mr. Aurousseau obtained a, granite-inclu- 

 sion, which he has handed to me for description. It differs from 

 the majority of the xenoliths in being merel}' accidental not cog- 

 nate with the including basaltic rock. It resembles the Gerringong 

 inclusions discussed above. It has suffered considerable jjressure, 

 the quartz is greatly strained, and there is some peripheral crush- 

 ing of the felspar-grains. These consist of large orthoclases, and 

 smaller less irregularly shaped oligoclases. A little decomposed 

 biotite is present. The whole rock has a dirty appearance, and is 

 clouded with dust, kaolin, sericite, magnetite, and a considerable 

 amount of carbonate. 



A granitic inclusion has been found in the volcanic neck at Nor- 

 ton's Basin, on the Nej^ean River, above Penrith. It also is greatly 

 shattered and full of carbonate veins. The structure appears to be 

 crystalloblastic, rather than a normally aplitic one; though this 



* Les Enclaves des Roches volcaniques, p. 64. 

 t (j!e(jlogische-petrographische Verhaltnisse der Unigegend voii Rothan 

 iin bohmische Erzgebirge. Neu. Jahrb. fiir Min.Beil., Band xxiii., pp. 475- 

 527. 



