"Vol. 65.] AND MAGNESIAN ROCKS OP NEW ZEALAND. 367 



Occurrence of the nephrite. — Nephrite was known to the 

 Maoris to exist only in the river-beaches and glacial drifts of the 

 Teremakau and Arahura rivers and the neighbouring country. 

 Later, when the goldfields were opened up, it was found in the 

 drifts in considerable quantity by the miners, and it soon came 

 into demand for jewellers' purposes. Owing, however, to the iron- 

 stained and bleached surface of many of the boulders, there is no 

 doubt that a considerable proportion escaped notice and were 

 stacked during the shifting of the heavy boulders and covered over 

 by subsequent workings. Its existence is not known in quantity 

 in deposits south of the Kanieri district, although occasional pebbles 

 have been picked up. It was generally understood to occur in situ 

 in the ranges to the westward ; but no clear idea of the locality or 

 of its mode of occurrence was given, until the explorations of the 

 New Zealand Geological Survey in 1906. In the Griffin Range it 

 occurs, as already stated, in nodules and veins, varying in thick- 

 ness from a few inches to a foot or more, in a mass of serpentine 

 talc-carbonate rock. It has not yet been observed in serpen- 

 tine masses, and appears to be always accompanied by talc and 

 carbonate, notably calcite. From the ranges the tough masses, 

 freed from their soft matrix, were transported, during the 

 Pleistocene extension of the glaciers, by the ice which filled the 

 river-valleys, until they found a resting-place in the glacial and 

 fluvio-glacial drifts deposited on the coastal plain. 



Hochstetter [2] and Dr. Dieseldorff [5] both record nephrite 

 from D'Urville Island, and the latter also from Stephen's Island in 

 Cook Strait. One of Dr. Dieseldorff's specimens was enclosed in 

 serpentine, but no description of its occurrence in situ is available. 



General Description of the Nephrite. 



Specific gravity and hardness. — The specific gravity of 

 the mineral varies from 2-95 to 3*05, the average density of pure 

 specimens ranging between 3*00 and 3*04. A series of deter- 

 minations made on different varieties of New Zealand nephrites 

 showed no definite variation of density in the different types. 



The same remark applies to the hardness. The hardness of 

 translucent and opaque, of pale and dark specimens alike, stands 

 at 6-5 (Mohs's scale), and no uniform variation can be detected. A 

 fractured surface is softer, its hardness varying from 4*5 to 6 ; but 

 the tests for hardness were made on polished surfaces crossing the 

 grain or cleavage of the specimen. Examination of specimens 

 split and polished parallel to the cleavage gave practically the same 

 figure, 6-5. It appears, therefore, that the direction in which a 

 specimen is cut has little influence on its hardness, provided that 

 in each case a polished face be tested. 



Structure. — The typical structures of the mineral, as examined 

 in the hand-specimen, are two, namely: (a) slaty or fissile 



