ORIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 133 



bear and dip in a manner that points to them as being formed 

 around a common centre, towards which they mostly all underlay. 

 This has been believed by Mr. Jack to have been caused by a 

 sudden depression having taken place near the central point, and 

 thus to have formed a system of fissures surrounding it that in 

 most cases dip towards the centre. I give a plan of three reefs 

 (Fig. 19) shewing their dip and strike, and also a cross section of 

 the reefs after Mr. Jack's plan. 



Fig. 20 is a cross-section of St. . Patrick's lode, and it is largely 

 impregnated with iron pyrites, which yielded as much as five 

 ounces of gold to the ton of ore when first struck, but afterwards 

 fell off to about two ounces ; where decomposed in the upper 

 levels it yielded about the same as the latter, viz., two ounces of 

 gold to the ton of ore. This lode altered its underlay very much 

 in one place, even curling upwards for some distance, as in Fig. 2 1 . 



Fig. 22, which is a cross-section of the Rainbow Reef shews the 

 lode between the walls to consist of broken granite on the 

 footwall, quartz without pyrites next, and quartz with pyrites on 

 the hanging wall ; both these lodes are evidently of the true 

 fissure class, and interesting examples of such as gold veins. The 

 mineralized or pyritous portion of the lodes are the richest in gold, 

 and expensive machinery to treat pyritous ore exists on this 

 field, and is continually being added to. Large quantities of 

 comparatively poor pyritous tailings lie in heaps at the various 

 crushing plants awaiting the day when improvements in the 

 process of treatment will make them capable of being rendered 

 remunerative. 



The G-ympie Reefing Field is noticeable for the fact that the 

 lodes depend upon the character of different bands of rock they 

 pass through for the extent to which they are auriferous. 



Bands of black slate occur with diorite and other rocks, and 

 it is when passing through this black slate that the lodes 

 contain most gold; being comparatively* poor in other parts. 

 Four bands of this black slate are known to exist, and so 

 dependent are the reefs on it that the miners first sink to 

 cut the slate and then drive to where a reef passes through it, 

 and start to work the lode at that place. 



The Rockhampton lodes are of a very pyritous character in 

 most instances, and perhaps the most remarkable gold mine in 

 the whole of Australasia, and also in the world that has ever been 

 found during modern times — is situated about eighteen miles 

 from Rockhampton, and is known as the " Mount Morgan Gold 

 Mine." Having visited it lately for the purpose of examining it 

 and the surrounding country, I can describe it as follows : — 



The country consists of altered sedimentary strata intersected 

 by numerous dykes and intrusive masses of a variety of igneous 



