794 GENERAL GEOLOGY OF MARULAN AND TALLONG, N.S.W., 



The different hardnesses of the various bands produce a verjr 

 striking effect on weathered surfaces. On the eastern boundary 

 of tlie western limestone-belt, where the grano-diorite is closer 

 to the contact, the alteration is more profound; the limestone has 

 been recrystallised to a dense white marble, with abundant 

 silicates — colourless wollastonite, and yellowish-brown grains of 

 garnet. 



The tongue of eruptive rock which extends southwards from 

 the main mass along the edge of Barber's Creek gorge, has 

 altered the eastern band of limestone much more profoundly 

 than the western one. At a point east of the lime-kilns, the 

 whole width of the belt consists of extremely coarse, saccharoidal 

 marble, the grain-size approaching 2 centimetres in places. In 

 its superficial portions this marble is very friable, but boulders 

 found in a creek which passes through it, indicate that, below 

 the limits of surface-weathering, it is dense and snow-white. 



Traced in a southerly direction, the metamorphism gradually 

 decreases, though even at Bungonia Caves, 4,000 yards from the 

 grano-diorite contact, the rock is still somewhat crystalline. 

 Traced in a northerly direction, the saccharoidal character con- 

 tinues almost up to the contact. The actual contact-line is 

 indefinite, as there is a band of silicate rock passing gradually 

 into marble on the south, and into grano-diorite on the north(see 

 p.799). 



A similar type of alteration, on a smaller scale, is met with at 

 the small patch of limestone to the east of Barber's Creek Falls. 



The slates and quartzites of the Barber's Trig, mass are con- 

 siderably metamorphosed round their eastern fringe, being con- 

 verted into dark hornstones. 



Certain small patches of dense white quartzite occur quite 

 irregularly over the surface of the limestones, just to the south 

 of the lime-kilns. These do not form connected beds or veins in 

 the limestone-series, but seem to occur quite sporadically. I 

 am of opinion that they represent small undenuded remnants of 

 Permo-Carboniferous quartzite formed in the same way as those- 



