BY W. N. BENSON. 535 



Sufficient field-work has not been done to ascertain whether 

 the quartz veins are continuations of granitic veins; the two 

 granite veins traced do not pass into pegmatite or quartz. This 

 point appears to be well worth investigating in view of the 

 differences of opinion that exist as to the origin of pegmatites. 

 Also, were the quartz veins shown to be connected with the 

 granitic intrusion, it would completely settle the question as to 

 the relative ages of andesite and granite. 



At the Caloola Gold Mine there is in the slate a large fissure 

 some 30 feet across, and extending probably to a great depth. 

 This is filled up with soft mud in which are embedded rounded, 

 and apparently waterworn, pebbles of various rocks, some rather 

 similar to the Devonian quartzites. It seems probable that this 

 is a fault crush-conglomerate. 



Also at Caloola is the carious feature of a highly crumpled 

 slate lying between walls of quite straight laminated rock. The 

 dip and strike of the slate varies greatly within a hundred yards 

 of the mine, but broadly it may be said to be easterly at 45°. 



To describe these slates petrographically, they can be divided 

 into seven distinct groups with varieties, each of which has a 

 sufficient!}'- characteristic appearance in hand-specimen to dis- 

 tinguish its members; and also each group or variety possesses 

 an almost constant microscopic character. Each group may be 

 described in order, dealing with its petrography and distribution 

 in the field; and an attempt will be made to show the origin of 

 each kind of slate. The seven groups are : — 



Blue Slate (varieties. Green Slate and Oxidised Slate), Quartz 

 Schist, Augen Slate, Fel spathic Slate, Knotted Slate (variety, 

 Spotted Slate), Chiastolite Slate, and Mica Schist. 



i. Blue Slate. — Macroscopic characters: hard, fissile, blue, fine- 

 grained; thin flakes have a translucent green colour and semi- 

 lustrous waxy appearance. Some specimens have small cubes of 

 pyrites developed. In the field this rock goes in a narrowing 

 band southwards. It forms the whole hill in which the slate 

 quarry (on Portion 42, Parish Galbraith) is situated, and runs 

 down along Back Creek nearly to Newbridge. Jt also goes north 



