164 



PROT. T. T. GKOOM ON THE IGNBOFS KOCKS [Feb. I9OI, 



Micrographic amphibole-augite phenoerysts. — In addi- 

 tion to the simple phenoerysts of amphibole and augite, there are 

 a small number of tabular phenoerysts in at least two of the rocks 

 (M 209 & M 101a) in which these two minerals are intergrown in 

 an intimate manner. A pseudomorph after amphibole with a 

 resorbed border may sometimes be seen to include a number of 

 fragments of augite, all extinguishing together (text-fig. 4, p. 163, & 

 text-fig. 5, below). The substance of the amphibole in these cases 

 is replaced by bastite or serpentine. The bastite- and serpentine- 



Fig. 5. — A portion of M 101 a (camptomte). x 69 diam. 



The above figure shows a corroded amphibole, with scattered grains of inter- 

 grown augite, all extinguishing together. Three or four of these are seen m 

 the figure as dark patches in the lighter oval space on the right-hand side. 

 Most of the granules in the grouuclmass are augite ; the darkest represent 

 iron-ore. The flow-arrangement of the felspar-laths is seen in the immediate 

 vicinity of the phenocrjst. [From a photograph.] 



fibres run parallel to the vertical axis of the augite, whence it may 

 be concluded that the two original minerals had this axis at least 

 in common. In other cases which are apparently similar (fig. 6, 

 p. 165, & fig. 7, p. 167), the augite is more abundant, and is pene- 

 trated by a mesh work of fibrous serpentine ; and the resorbed border 

 is incomplete or absent. It is only short, stout, forms of amphibole 

 that appear to be intergrown with the augite, and apparently in 

 the main those that have been corroded. 



The f elspar-j)henocrysts are small, few in number, and 



