XXll PRESIDENTIAL ADDRESS. 



6 feet wide. Beautifully banded copper lodes, proved to a depth 

 of 200 feet may be seen at the Lady Mary and Cumnor mines, at 

 Montalbion. 



(2). /)///>•(' Ldilt's. — Characterised l)y the ore being associated 

 with intrusive dykes of igneous rocks such as elvans and diorite 

 dykes. They are true fissures, but the dyke rock forms the 

 boundary of the lode and the country rock lies outside. They 

 are as permanent as class 1. As examples we may cite the Great 

 Northern Tin Mine at Herberton, over GOO feet deep, in which 

 the tin ore seems to occur in irregular almost parallel shoots 

 cutting diagonally at steep angles across an altered diorite dyke. 

 The chief silver lodes at Dargalong similarly occur in a fine 

 grained dyke of hornblendic granite, and the Sun Rise group of 

 copper and silver mines, south of the Tate, are in dioritic dykes, 

 which in places become pure hornblende rock. 



(8), Carlxnuoi. I have adopted this term to designate the 

 irre*?ular copper and silver deposits which characterise the 

 Chillagoe area. They occur at or near the junction of the 

 granite with the other rocks, are sometimes of enormous dimen- 

 tions, and occasionally run almost uninterruptedly for over a 

 mile. They are irregular in all their dimentions, but being of 

 undoubtedly deep-seated origin they justify a large expenditure 

 in sinking. The typical gangue is eclogyte, and where ore- 

 bearing, are highly charged with iron. 



Where denudation has removed the adjacent limestone they 

 often form nuirked features in the landscape, standing up as 

 bluffs occasionally as much as iSO feet high and 200 feet wide. 



They are by no means confined to the limestone for I have in 

 over 50 places traced them downwards into the Herberton Beds. 

 It is, however, quite probable that in tlie limestone the carbonas 

 have larger dimentions than in the less solul)le Herberton 

 beds. 



Most of the Chillagoe mines are of this chariicter and it is 

 unnecessary to cite examples. 



(4). Iiiiiiiri/ndtiois fmm Faults. — In this class the ore has 

 been brought up through the faults and become disseminated 

 through the country. Hence there are no true walls, and the 

 mines are very indefinite and can only be proved by carefully 



