THE GEOLOGY OF YELSOX. 
Mowatt, whose south-eastern slope to a height of about 2000 
feet is composed of serpentine. In the bed of the Blarich 
River, Mr IXaast found a piece of copper ore of the same 
description as the Dun Mountain ores. 
On the western side, the serpentine occurs developed to a much 
greater extent. An immense serpentine dyke, of a thickness of 
several miles, stretches from the northern extremity of D 1 1Trville ’ s 
Island, across the Drench Pass, through the Croixelles, by the 
Dun Mountain and "Upper Wairoa, and is met with again, on 
a continuation of the same straight line, on the Red Hills, 
near the Top-house, on the northern side of the Wairau valley. 
This dyke can thus be traced from north-east to south-west for 
a distance of eighty miles. The strike of the serpentine dyke 
is perfectly parallel to that of the slates, but its eruptive origin 
is proved by the occurrence of a breccia of friction (Reibungs 
breccia) at the line of contact, and the fact of beds of slate 
enclosed in it being converted into hard and semi-vetrified 
cherts. The serpentine, in its turn, has been broken through 
by eruptive dykes of hypersthenite and gabbro. The rock of 
the Dun Mountain proper is a variety of serpentine, of so 
novel and peculiar a character that I am obliged to apply to it 
a new term, and call it “ Dunnite ” The Dun Mountain, 
district offers to the scientific geologist a field of unbounded 
interest; but I shall perhaps best respond to the wishes of my 
audience by telling them something about the ores of copper 
and chromate of iron which are the characteristic metals of 
that serpentine dyke. 
Copper. 
The occurrence of native copper, red oxide of copper, and 
copper pyrites, the principal copper ores of the Dun Mountain, 
is by no means peculiar to the serpentine of Hew Zealand. In 
the serpentine district of Cornwall, for instance, native copper 
is found. The Monte Ramazzo, near Grenoa, contains copper 
ores in serpentine, and in North America the same thing 
occurs. 
I have visited (accompanied by Mr. Hacket and Mr. *Wrev) 
all the workings of the Dun Mountain. I could not convince 
myself of the existence of a number of parallel lodes, so as to 
justify the various names which have been given, and which 
appeal to designate different lodes. The Dun Mountain 
