ADDITIONAL COMMENTS ON THE GEOLOGY OF THE JUAN FERNANDEZ ISLANDS 55 



Fig. 12. Lumps of magnesite ;the so-called Glockenstein . Nat. size. Rahia del Padre, Masatierra. 

 Reproduced from P. Quensel, 12, p. 269. 



Fig. 13. Scoriaceous lava with newtonite and bole. Nat. size. Bahia del Padre, Masatierra. 

 Reproduced from P. Quensel, 12, p. 269. 



will in this connection only summarize the facts. The rocks in question are very 

 fine-grained and of a greenish colour. The abundant cleavage plains are coated 

 with epidote and calcite. Pyrite is finely dispersed throughout the rock. Under 

 the microscope one can see that original phenocrysts of both olivine and augite 

 are more or less completely changed to serpentine and chlorite. The matrix con- 

 sists of olivine, augite, plagioclase, magnetite and ilmenite — i.e., the usual 

 mineral assemblage of the basaltic lavas. The greater part of the silicates are. 



