BY H. C. RICHARDS. IIT 



'• Hirschwald takes the binding number (Bz) to mean 

 the number of grains which appear to be combined with 

 each single grain in the plane of the transparent section, 

 and the measure of binding (Bm) is the quotient of the 

 sum of those portions of the grain-circumference which have 

 intergrown with the neighbouring grains and of the entire 

 circumference of the grain. While as a general rule the 

 number of texture pores increases with the ' grain binding 

 number." the size of the pores decreases with increasing 



measure of binding. The greater the quotient -^ the 



larger the areas on which the grains adhere to each other, 

 and therefore the more consideral^le the resistance opposed 

 by the grain adhesion to weathering agencies." * 



An attempt to apply this method to the several sand- 

 stones used in Queensland in the hope of drawing up a table 

 of comparative binding qualities has been unsuccessful 

 owing to the fact that in nearly all our stones the cementing^ 

 riiedium is so abundant tha-t it is frequently difficult to find 

 two sand grains in contact ono with the other. 



Breakfast Creek Sandstone. 



This stone was worked from the sixties to the eighties 

 of the last century in Petrie's and Brydon"s quarries on the 

 Reservoir Hill, abo\e Breakfast Creek, at Albion. 



Petrie's quarry in particular is a verj' extensive quarry 

 and a great deal of material has been removed. The 

 quarrj^ has been worked out now but an inspection shows 

 that there Avere beds of good thickness and that the joint- 

 ing of the stone was fairly regular and reasonably far apart. 

 Current bedding, hoAve\ er, is a particularly common feature 

 about the stone. 



The stone is a very friable, coarse, sandstone with 

 rather poor weathering properties. It has an average 

 grain-size of .5 mm. and is made up of quartz grains, rounded 

 to subangular, weathered felspar granules and occasional 

 secondary mica particles. Some of the cj^uartz grains are 

 built up of fragmentar}' quartz particles. The percentage 

 of felspathic cement is a cry large and considerably more 

 than 50% of the stone is cement (see microphotograph 



* Int. Ass. Testing Mats., ii. No. 11, July 15th, 1912. 



