BY W. X. BENSOX, W. S. DUX, AXD W. R. BROWXE. 409 



with frayed ends. Measurements indicate acid andesine, about Abes An32. There 

 is a second crystallization of microlitic felspar liiving approximately straight 

 extinction, which would point to olig'oelase. This forms a kind of mesostasis of 

 sub-variolitic aspect. The spaces between the felspars are tilled with a confused 

 mass of chlorite, some of which is pseudomorphous after a mineral giving rect- 

 angular sections, possibly ]iyroxene, while the rest is just interstitial and may 

 represent original glass. It is sprinkled with rod-like microlitic iron-ore. Car- 

 bonates are present in fair amount, both a-s little interstitial patches and also, with 

 quartz, tilling a few vesicles. The rock may provisionally be termed an andesine 

 basalt, though probably more acid than normal basalt. 



Specimen 1440, collected from Portion 57, a little south of the andesine basalt 

 just mentioned, is possibly from another interbedded flow. It is typically basaltic 

 in appearance, liluish-black, very comjiact and with a i-atlicr hackly frnchue. 



In thin section it is hypocrystalline intersertal and very fine grained. Laths 

 of bytownite, varying' from a length of .75 mm. down to microlitic dimensions, 

 and slightly altered, are distributed through a matrix composed of pyroxene and 

 magnetite. The pyroxene is a bright yellow-green colour and occurs in dense 

 masses of extremely tiny, rounded, and almost e(|uidimensional granules and 

 crystals. Some of these are distinctly pleochroic and have straight extinction, in- 

 dicating hypei-sthene, but the bulk of the pyroxene is augite. There is abundance 

 of magnetite as tiny crystals and locally as clouds or patches of fine dust. 



The relative proportions of the different constituents vary very much from 

 point to point in the slide, but on the whole felspar probably predominates, with 

 pyroxene and magnetite in the order given. There are fairly frequent in-egular 

 small patches of altered brown glass into which felspar and pyroxene crystals 

 protrude, and in the neighbourhood of these patches minerals may be rather lai'ger 

 and more idiomorphic than usual. Minute apatite needles are scarce. Occa- 

 sional aggregates of magnetite with some indeterminate material, up to 2 ram. in 

 length, appear to be pseudomorphs, possibly after olivine. This may be called a 

 hypocrystalline intersertal basalt. 



Basalts of the Verrie Series. 



For the most part the rocks are very decomposed, and only one specimen 

 (1510) was available for sectioning (PI. xxv., fig. 9). This was obtained from a 

 well in Portion 239, at the head of Anstey's Creek. It is a rather weathered, grey,, 

 fine-grained rock, amygdaloidal in structure, the vesicles being filled sometimes with 

 calcite and sometimes with white or colourless zeolites. Under the microscope 

 the rock is seen to have suffered considerably from surface alteration. The prin- 

 cipal constituent is a plagioelase, in laths averaging about .8 mm. long which 

 are at least as basic as labradorite. There are occasional traces of parallel orien- 

 tation, and the interspaces between the felspars are filled largely with augite which 

 is interstitial rather tlian ophitic. It is of a greyish-l)rown colour, very faintly 

 pleochroic, and has magnetite plentifully distributed through it. What were pro- 

 bably small crystals of olivine are now represented by aggregates of serpentinous 

 material always rimmed with translucent haematite. Evidently the original olivine, 

 if such it was, was highly ferriferous. Further alteration of the rock is indicated 

 by interstitial patches of fibrous radial green chlorite. The amygdules are filled 

 with quartz crystals and calcite, or with calcite and a zeolite which may be cha- 

 bazite. 



