Park. — Thermal Activity and Metalliferous Veins. 22 



The hot springs give ofl' large quantities of H 2 S, and occa- 

 sionally a little steam. The gas escaping through the water 

 of the pools and small streams is partially oxidized, liberating 

 sulphur, which imparts a milky-white colour to the pools, 

 locally known as -'white lakes." The beaches of the so- 

 called " white lakes " consist of sulphur mixed with magnetic 

 ironsand and a small proportion of alum. Sulphur is also 

 being sublimed at the vents or openings in the rocks from 

 which H 3 S and S0. 2 gases escape. 



The prospecting- work conducted by Griffiths disclosed 

 some interesting features. A deposit of cinnabar and pyrites 

 crops out at tbe foot of the hills to the south-west of the 

 main deposits. A shaft was sunk near it, and cut the lode 

 at a depth of 35 ft. The ore was 2 ft. thick, and consisted of 

 small crystals of pyrites cemented by cinnabar. At this 

 depth there was a strong evolution of H 2 S, and the heat of 

 the rocks increased so rapidly with the depth that mining was 

 extremely difficult. 



It is noteworthy that the outcrop of this lode was found 

 close to the charred trunk of a tree partially imbedded in hard 

 siliceous mud. The trunk and roots of the tree were coated 

 with a thin film of cinnabar, as also were some pieces of fossil 

 kauri-gum found near the roots. 



A small trench was sunk over a small fumarole ; and at a 

 depth of 10 ft. the temperature of the rock was found to be 

 185° Fahr. 



No. 1 borehole, cased with 3 in. piping, was put down to a 

 depth of 104 ft., where it encountered the edge of the basalt. 

 At the same time it struck a fissure from which hot mud was 

 projected a height of 60 ft. for about forty-eight hours. The 

 mud was succeeded by boiling water charged with H 2 S gas, 

 which was found to issue at a pressure of 30 lb. per square 

 inch. 



Griffiths further mentions that the richest deposits of cin- 

 nabar were found in close proximity to the hottest fumaroles, 

 and that at very shallow depths a temperature was soon 

 reached which precluded mining operations being carried on. 



The Ohaeawai hot springs cinnabar-deposits, although 

 never likely to be turned to economic account, are of great 

 scientific importance from the light which they throw upon 

 the formation of sulphide ores by solfataric actions. The 

 deposits are still in process of formation, and metallic sul- 

 phides have been, and are still being, deposited in under- 

 ground fissures and at the surface, together with the sinters 

 which form the matrix. 



The hot springs and fumaroles owe their existence to the 

 eruption of the basalt, but the basalt is manifestlv not the 



