274 Transactions. 



SoUas (11, vol. 2, pp. 13, 14) describes a sample of rock from the Black 

 Hill as a light-grey hyalopilitic andesite, with hornblende and biotite. He 

 also mentions the possible presence of quartz and tridymite. 



The Black Hill andesite contains in places small fine-grained segregations. 

 One of these on microscopic examination exhibits numerous small feldspar 

 laths of rather basic type (labradorite), together with small phenocrysts of 

 augite, chlorite, and plentiful magnetite imbedded in a glassy base. The 

 structure is reminiscent of an ordinary basalt. The transition border con- 

 sists of large feldspars near andesine, with some hornblei>de, enstatite or 

 hypersthene (near bronzite), biotite, and quartz (very rare) imbedded in an 

 obscure apparently more or less glassy base. 



One section of a rock from a spot on the east side of the Ohinemuri 

 River aboiit a mile and a half north-east of Waihi shows a hornblende- 

 andesite with some biotite, augite, and hypersthene (rare). A second 

 section contains more hypersthene, but less augite and biotite. It thus 

 approaches very nearly the Black Hill rock described by Sollas. 



About two miles and a half west of Waihi, along the course of the water- 

 race to the Victoria Battery (Waikino), there occurs a hornblende-andesite 

 with some augite and enstatite (or bronzite). The two sections made differ 

 considerably in the relative proportions of rhombic pyroxene, so that a 

 want of homogeneity in the rock-mass is again apparent. 



Literature. 



(1.) 1871. Hector, James. " On the Geology of the Cape Colville Dis- 

 trict." Rep. N.Z. Geol. Surv. during 1870-71, vol 6, pp. 88-103. 



(2.) 1883. Cox, S. H. " Goldfields of the Cape Colville Peninsula." Rep. 

 N.Z. Geol. Surv. during 1882, vol. 15, pp. 4-51. 



(3.) 1897. Park, James. " The Geology and Veins of the Hauraki Gold- 

 fields." Trans. N.Z. Inst, of Min. Eng., vol. 1. 



(4.) 1897. McKay, Alexander. " Report on the Geology of the Cape Col- 

 ville Peninsula, Auckland." Mines Report, C.-9, pp. 1-75. 



(5.) 1899. Park, James, and Rutley, F. " Notes on the Rhyolites of the 

 Hauraki Goldfields, New Zealand." Quart. Jour. Geol. Soc, vol. 45, 

 pp. 449-69. 



(6.) 1900. Park. James. " Notes on a Hypersthene-andesite from Waihi 

 Mine, Waihi." Trans. N.Z. Inst., vol. 33, pp. 342-43. 



(7.) 1902. Morgan, P. G. " Notes on the Geology, Quartz Reefs, and 

 Minerals of the Waihi Goldfield." Trans. Aust. Inst. ' Min. Eng., 

 vol. 8, pp. 164-87. 



(8.) 1904. Morgan, P. G. " W\ater in the Hauraki Goldfield." Eng. 

 and Min. Journ. of New York, vol. 78, p. 429 (15th September). 



(9.) 1905. Lindgren, Waldemar. " The Hauraki Goldfields, New Zealand." 

 Eng. and Min. Journ. of New York, vol. 79, p. 218 (2nd February). 

 Reprinted in " New Zealand Mines Record," vol. 8, pp. 370-73 

 (17th April). 



(10.) 1905. Morgan, P. G. " The Hauraki Goldfields, New Zealand." 

 Eng. and Min. Journ. of New York, vol. 79, p. 861 (4th May). Re- 

 printed in " New Zealand Mines Record," vol. 8, pp. 465-67 (16th 

 June). 



(11.) 1905-6. Sollas, W. J., and McKay, Alexander. " The Rocks of 

 Cape Colville Peninsula, Auckland, New Zealand." 2 vols. 



