A SriJERULITIC DOl.EIUTE FKOM VRYHEID, NATAL. 387 



There appears to he no marked relation between tlie 

 positions of the enstatite and augite phenocrysts and the 

 general radial structure. Here and there a crystal of 

 enstatite is seen to be broken across, and the several parts 

 are separated by a small interval as though pushed apart by 

 tlie outgrowing felspars. In places the augites appear to 

 have conceutrated in the eddies between two streams of 

 felspars, and very occasionally the crystals lie witli their long 

 axes parallel to the laths; in nearly every case, however, the 

 positiou of the augite is quite independent of the radial 

 structure. 



All the above phenomena can be readily made out with a 

 2-inch objective, but the application of a higher power 

 brings to light further interesting facts. 



The interspaces between the felspars are, as above 

 mentioned, occupied by a pale yellow augite and minute 

 crystals of magnetite. This augite is not in granules but in 

 more or less continuous crystals, which appear to be very 

 closely intergrown with the felspar, even at the centres from 

 Avhich the latter starts (PL XXX, fig. 1). The secondary 

 zone of augite at the edges of the phenocrysts frequently 

 presents a serrated edge, indentations being formed to receive 

 the ends of the felspar crystals which abut against the augite 

 phenocrysts; consequently, in the neighbourhood of these 

 phenocrysts the felspars are wrapped about by minute ophitie 

 plates. It is impossible to make any distinction between the 

 augite of these secondary zones and that filling- the inter- 

 spaces between the felspar (PI. XXX, fig. 2). 



We undoubtedly have in this rock an example of the 

 pseudo-spherulites of Rosenbusch, and these spherulites are 

 of a truly remarkable size for so basic a rock. Nearly all 

 spherulitic (or variolitic) structures hitherto described in 

 basic rocks are contact phenomena produced in the glassy, or 

 devitrified glassy, facies of andesites or basalts. The spheru- 

 lites are usually of very small dimensions, and have often 

 suffered considerable alteratiou. 



However, an occurrence of "a coarsely spherulitic (S'ario- 



