Plate 20 



Photomicrograph of specimen no. 115. BasaU. Taken with plain light, 

 magnification about 50 diameters. 



Taken to show the fine felsitic ground mass habit of this rock with its 

 slightly porphyritic texture and its rather numerous rehealed fractures. 



The rock is not recrystallized and not sheared, but it is fractured and 

 rehealed and somewhat altered. 



Plate 21 



Photomicrograph of specimen no. 57. Dunite. Taken with plain light, 

 magnification about 30 diameters. 



Taken to show the structure and make-up of this very unusual specimen. 



1 The principal constituent is olivine 



2 The flaky shreds are antigorite 



3 The black spots are magnetite 



