GEOLOGY OF THE JENOLAN CAVES DISTRICT. 343 



fracture displays a lustrous surface due to the presence of 

 minute mineral particles which have resulted from regional 

 metamorphism. They are for the most part thinly bedded, 

 but some massive strata also occur. Professor David has 

 referred to the occurrence of doubtful Radiolar la in some 

 of these slates, but otherwise they are unfossiliferous. 

 This question of the occurrence of Radiolaria has not been 

 further investigated by us. 



Quite apart from the small amount of contact meta- 

 morphism shown at their junction with the intrusive igneous 

 rocks to be referred to later, they exhibit a*varying amount 

 of regional metamorphism which has resulted in the 

 development of minute crystals of secondary minerals. 

 These are too small to be seen in hand specimens, but their 

 presence is indicated by the lustrous surfaces given when 

 the rock is split. Denudation has not cut deep enough into 

 the Jenolan anticline to reveal the true thickness of these 

 slates, and owing to the extent to which they have been 

 intruded by later igneous rocks, it is difficult to determine 

 the thickness of that portion exposed, but it must be at least 

 2000 feet. Excellent exposures of these slates can be seen> 

 along the cuttings of the Mount Victoria-Jenolan Road, 

 quite close to the Grand Arch. 



The association of limestone and slates at Jenolan, and 

 the particularly favourable conditions for quarrying them,, 

 would give ideal conditions for the manufacture of Portland 

 cement, were it not for the great difficulty of access, 

 owing to the very rugged nature of the country between 

 here and the nearest railway-line. 



3. The Quartzites. — These are almost pure white in 

 colour, are very fine-grained and more or less argillaceous; 

 they are also thinly-bedded and much jointed. They out- 

 crop extensively along the bed of Jenolan River immediately 

 to the east of the eastern bed of limestone, where they lie 



