PLATE XXVI. 



AUGEN-GABBRO. 

 (Natural size). 



KARAKCLKWS. 



This plate represents the appearance of a polished surface of foliated gabbro. 

 The "eyes" are formed of diallage. The dark bands are mainly composed of 

 green hornblende ; the white bands and streaks of the so-called saussurite. 



The white spots seen in certain parts of the plate represent an undetermined 

 substance which is almost constantly present in the Lizard gabbros. It appears 

 in the glassy felspar of the comparatively unaltered rocks and increases in amount 

 as the felspar passes into the condition of saussurite. 



The parallel structure in this rock is regarded by the author as the result 

 of the deformation by earth-stresses of an original mass of normal gabbro. 



The slab is traversed by narrow veins which cut the planes of foliation at 

 angles of about 15. 



