View of Castle Hill and Coromandel Harbour. 
tlieir mouths and on the coast are inconsiderable. The coast con- 
sists of nothing but trachytic breccia and tuff, in the most varying 
colours and in the most different state of decomposition, from the 
hardest rqck to a soft clayish mass, and in various places broken 
through by doleritic and basaltic dykes. Silicious secretions in the 
shape of chalcedony, carnelion, agate, jasper, and the like, are a 
very frequent occurrence in these tuffs and conglomerates , likewise 
large blocks of wood silicified and changed to wood-opal. By local 
geologists those trachytic rocks were erroneously taken for granite 
and porphyry , and by a gross mistake the most sanguine hopes 
wei’e based upon the notion that these silicious secretions might be 
auriferous quartz veins. 
The Coromandel gold originates from quartz reefs of crystal- 
line structure, belonging to a palaeozoic clayslate formation , 1 ot 
which under the cover of trachytic tuff and conglomerate the 
mountain range of Cape Colville peninsula consists. The mountains 
are so densely wooded that it is only here and there in the gorges 
1 The same clayslate formation constitutes the Hunua range in the brown coal 
district South of Auckland near Drury and Papakura, and continues towards South 
and North to a great distance. It is but very recently (May 1862) that traces of gold 
are also said to have been discovered in the Hunua district. 
