ON THE RUCKS OF TIIR IIAURAKI GOLD-FIELDS. 263 



ten enstatite aude.sites the majority are dykes. So that, in a 

 broad way, it may be said that the auriferous series consist of 

 lava streams, chiefly augite andesites, pierced by dykes of horn- 

 blende and enstatite andesite. 



Three other rocks which I obtained deserve a slight .separate 

 notice. 



7. — Enstatite andesite from the three hundred and tliirty feet 

 level of the Prince Imperial Mine. This is the rock through which 

 No. 2 reef runs. This reef averages from six inches to two feet 

 in tliickness, and has yielded large quantites of gold. Foi' about 

 fifty feet on each side of the reef the rock is decomposed, and tliere 

 is no distinct boundary between the hard and the soft. At this 

 level the hard rock above the reef is tifty feet thick, and that 

 below the reef sixty feet. The whole thickness, including the 

 reef and decomposed portions, being two hundred and ten feet. 

 At the live hundred and sixty feet level the lower portion of the 

 hard rock disappears, whether tlie upper one does so also is not 

 yet known. These hard belt* (called diorite by Mr. Cox) are 

 formed by a greenish-black rock with abundant small felspars 

 visible to the eye. The ground-mass is fairly abundant, pale brown 

 with chloritic infiltrations. The plagioclases are clear or slightly 

 decomposed. Of the augites some are fresh but others are altered 

 into a bluish-green chlorite, partly isotropic and partly with low 

 polarization colours. Bastite is in long rectangular prisms, strongly 

 pleochroic, and with fairly brilliant polarization co'ours. Mag- 

 netite is abundant in grains. Pyrites is rare. [ take this rock 

 to be a lava stream. S.G. = 2.729. 



8. — ^Chloritic augite andesite from the three hundred feet level of 

 the Waiotahi Mine. It is a greenish-grey rock vvith opaque white 

 spots of leucoxene and with a rather earthy fracture. The ground- 

 mass is abundant, devitrified, and infiltrated with chlori'-e. The 

 felspars are decomposed into a colourless aggregate of calcite and 

 perhaps kaolin. A brownish-green chlorite forms pseudomorphs 

 after augite ; it is partly isotropic and partly shews grey polariza- 

 tion colours. Secondary quartz is scattered sparingly through 

 the ground-mass. Leucoxene is abundant in small specks thi'ough 

 the ground-mass and in large white spots. Pyx'ites is in small 

 quantity but there is no magnetite. This is the typical 'tnfanite' 

 of Sir James Hector.*" It is also the rock mentioned by Mi'. Cox 

 in his report of 1882 (p. 9, No. 54) as having " a dioritic appear- 

 ance but seems to be mechanically formed." This deceptive 

 appearance is due to the leucozene spots which often look like 

 rolled fragments of a white felspar. Undoul:)tedly the rock is a 

 decomposed lava stream. S.G. = 2.590. 



* Reports Geological Explorations, 1870-71, p. 147. 



