BY W, ISr. BENSON. 615 



The agglomerate of Housefield's Hill, in the centre of the 

 Parish of Woolomol, contains approximately the same variety of 

 boulders. The peculiar strained quartz-keratophyre is found 

 also as a dyke beside the hill. The waterworn appearance of the 

 pebbles and boulders is especially marked in this locality. 



Seiyeyitines. 



The majority of the serpentines seen are similar to the rocks 

 described in the earlier paper(16), and do not call for any further 

 comment. One specimen, however, from Portion 118, Parish of 

 Nemingha, is of special interest. It is a typical example of a 

 serpentine derived from diallage The chief constituent of the 

 rock is antigorite, which in some places exhibits the " gitter- 

 struktur" perfectly, but is more usually distributed rather irregu- 

 larly, or grouped into radiating masses. Some residual diallage 

 is present, into which the antigorite cuts sharply, either as irregu- 

 larly placed blades, or in lines parallel to a cleavage. The last 

 remnants of the diallage are cloudy grey matter. Small ribbon- 

 like veins and irregular patches of fibrous anthophyllite(?) are 

 also present, sometimes stained brown and matted, but never 

 notably pleochroic. The anthophyllite-fibres may stretch across 

 the whole width of the vein, or may grow out unevenly on either 

 side of a narrow crevice. Very irregularly shaped masses of 

 magnetite are scattered about. 



Associated with the serpentine is a little gabbro, which has 

 also been described; it is remarkable for the replacement of its 

 felspar by zoisite. One specimen contained olivine and hyper- 

 sthene, two minerals which are rarely seen in the gabbros in the 

 Great Serpentine Belt. (See 16, pp. 683-4). 



Dykes of Dolerite in the Serpentine. 

 A number of these have been studied, and found to correspond 

 exactly with those described from the north side of Chrome Hill, 

 Bowling Alley Point, of which an analysis has been made 

 (17, p. 139). According to the extent of the development of 

 brown hornblende, the rocks may be classed as dolerites, with 

 little hornblende, and proterobases, in which it is more abundant. 

 The hornblende, however, is alw^ays subordinate to the augite. 



