NICKEL-IRON ALLOT AWARTJITE OF NEW ZEALAND. 629 



thin sections cut from a specimen at various angles. These sections 

 look under the microscope much like those prepared of Red-Hill 

 rock similarly constituted ; the only difference being a more pro- 

 nounced brownish-yellow colour of the enstatite and a greater 

 quantity of dark ore-grains (chromite &c.). In one section, how- 

 ever, there are seen four small, irregularly-outlined grains of a trans- 

 parent green mineral, which certainly is monoclinic, though whether 

 it be hornblende or a pyroxene optical examination leaves undecided. 

 Two of the grains, showing a few parallel cleavage-cracks, and 

 parallel to these a slightly fibrous structure, extinguish one at 

 an angle of about 12°, the other at about 17° with these cracks, 

 and are slightly pleochroic, changing from bluish green to yellowish 

 green ; the third grain shows only irregular cracks and hardly any 

 pleochroism ; but in the fourth grain, rendered rather dusky by fine 

 black dust, there are a few, though very indistinct, cracks, apparently 

 crossing each, other at approximately right angles, and the extinction 

 makes nearly equal angles with these cracks ; it is feebly pleochroic, 

 the green colour becoming fainter. The employment of conver- 

 gent polarized light gave no definite results for any of the grains. 

 Accepting the cracks in the fourth grain as really indicating cleavage, 

 the mineral is doubtless a pyroxene, and probably diallage. The 

 specific gravity of the rock is 3- 17-8*35, and its chemical com- 

 position, according to a bulk analysis by Mr. Thomas Batement, as 

 follows : — 



SiO, 39-99 



Al^Og 3-55 



Cr^Og Strong traces 



EeO 8-56 



MnO traces 



CaO 4-19 



MgO 41-26 



H.O 2-07 



99-62 



Among the specimens from the Cascade Eiver at the foot of 

 the Olivine Eauge are pieces of a hard nephrite-like serpentine 

 (bowenite ?), containing small specks of Awaruite embedded in it. 

 The specimens are evidently portions of rolled pebbles. 



3. Mode of Occurrence and Distribution of the Awaruite. 



The first sample of the Awaruite-bearing black sand examined by 

 Mr. Skey was supposed to have come from Barn Bay (p. 619) ; but 

 it was subsequently proved to have been washed from the drift of 

 the Gorge Eiver. The valley of this river has since generally been 

 considered to be the only place of occurrence of the mineral, and is, 

 indeed, the one in which it has so far been proved to exist in largest 

 quantity. Mr. U. Mueller, the Chief Surveyor, in answer to my en- 

 quiries on this point, states : " The mineral is found in the bed and 



