GEOLOGY OF YASS DISTRICT. 109 



the ranges near Mt. Hawkins many examples of sedimentary rocks 

 enclosed in the porphyry are to be seen, and it will be interesting to 

 find out the thickness of the beds which have been absorbed by this 

 porphyiy if it is an intrusive. In the same railway cutting at 183 

 mile peg it will also be noticed that the porphyry is decidedly 

 columnar in nature ; so much so that in making the line many of the 

 columns have been thrown on one side, and are still to be seen near 

 the fence. (PL III. Fig. 2.) This prismatic jointing is a peculiarity 

 common to some of the Yass porphyries, but so far none have been 

 seen to equal the examples to be found here. 



Bango Beds. — The boundaries of the Bango Beds both east and 

 west are so intimately mixed with the porphyries, that it has been 

 impossible to decide their extent. If the porphjn-ies are intrusive, 

 a large proportion of the silurian sediments have been engulphed 

 by them, leaving at this part of the section only a very narrow strip 

 of unaltered rocks. The paucity of outcrops of this horizon has 

 resulted in its being entirely overlooked from a geological point of 

 view, although when the southern railway line was being constructed 

 in 1876 an outcrop of a beautiful white limestone was discovered, 

 and a practical use made of it by burning for lime used in the 

 construction of the culverts. Intermittent lime burning has been 

 carried on ever since. 



Attention was first drawn to these beds in 1905, when I went 

 at the request of a Yass syndicate to Coolalie to report on the suit- 

 ability of an outcrop of marble on portion 22, Parish of Bango, as a 

 lime burning industry. The quarry is about a mile to the north 

 of Coolalie Railway Station, and has been known locally as the 

 Coolalie marble quarry. As, however, this name is liable to be con- 

 founded with Caloola, near Bathurst, I have thought it advisable 

 to refer to the horizon as the Bango beds. I have found outcrops 

 in portions 56, 22, 19, 17, and 123, the strike of the beds being 

 about 20° W. of N. I have also seen what I consider to be a con- 

 tinuation of the same beds in portion 3, Parish of Blakney, on the 

 same line of Strike. The intervening country where flat shows no 

 trace of limestone, which no doubt is covered with recent deposits. 

 In the hilly country it is hidden, if not altogether absorbed by the 

 porphyry. 



Where the deposit has been worked for lime, in portion 22, 

 Par. Bango, the stone varies from a coarsely crystalline marble 

 to a close gi"ained limestone, of many shades of colour, ranging from 

 a pure white to dark mottled red and grey, with occasional patches 

 of shades of gold and iron grey. Some of these marbles are very 

 handsome when polished, but no attempt has been made to work 

 the deposit on any other basis than as a lime quarry, and blasting 

 being the only method used to extract the stone, the face of the 

 deposit has been badly starred and fractured. The lime from this 

 quarry, on account of its extra quality, is in great demand ; 

 but, owing to the primitive methods of burning, is not turned out as 

 rapidly and regularly as is necessary to supply a big market, 

 consequently the industry is not as flourishing as it should be. 



