GEOLOGY OF THE COOMA DISTRICT, N.S.W. 185 
gneiss. It is however devoid of gneissic banding, and has 
more of the appearance of a felspathic porphyry. 
Amphibolite.—In the town of Cooma, 200 yards or so 
south of the R. C. Church, is an outcrop of amphibolite 
intrusive into the Cooma gneiss. The main outcrop is of 
rudely circular form, and about 50 yards in diameter. The 
rock consists largely of coarse amphibole crystals up to # 
of an inch long, medium and fine-grained modifications 
occurring in subordinate association. The first two kinds 
are massive, but the fine-grained rock is in places notably 
schistose, with bands of fine pegmatite running parallel to 
the schistosity. The mutual relations of the three varieties 
are obscure, the grainsize changing abruptly without any 
apparent reason. 
Interstitial white material in the coarse and medium- 
grained varieties probably represents felspar. Apophyses 
from the main mass are thrown out to both north and south; 
medium-grained amphibolite is found in the street between 
the R.C. Church and Convent, and a narrow dyke can be 
traced for upwards of halfa mile tothe south. Pegmatite 
veins seam the main outcrop in all directions, and the 
southward dyke is generally in close proximity toa narrow 
vein of pegmatite. 
Small isolated patches of amphibolite, usually not more 
than a yard or two in diameter, are found. One is on the 
north side of the Berridale road at the first rise out of 
‘Cooma, having associated with it ill-defined dykes of fine- 
grained amphibole schist; another occurrence of coarse- 
grained rock is at Pine Valley, a little north of the Berri- 
dale road, and a third has been noticed to the west of the 
Mittagang road, near the S.W. corner of Portion 108. These 
last two occurrences, like that in the town of Cooma, are 
closely associated with pegmatite veins: the probable 
significance of this will be discussed later. 
