CHAPTER XXIV 



PALAGONITE 



From the sea-border to the mountain-top in almost every part 

 of the island, palagonite occurs in a fragmental condition. It is 

 only where tuffs are not found, as in the mountainous mass of 

 Seatura, or where these deposits are formed of acid rocks as in the 

 north-east portion of the island, that palagonite has not been 

 observed. Perhaps, it is not too much to say that the later if not 

 all the stages in the history of Vanua Levu are bound up with the 

 history of this material. In this place I will only deal with certain 

 features in the problem connected with the origin of palagonite 

 which seem to receive further elucidation from my observations in 

 this island. The literature is already extensive, and those inter- 

 ested in the matter will find in Zirkel's PetrograpJiie and in the 

 Challenger Report on Deep-Sea Deposits by Murray and Renard 

 a good introduction to the subject. 



In Vanua Levu we are confronted with the same difficulty that 

 has perplexed geologists in various parts of the world. If we 

 expected to find in this island the source of the enormous quantities 

 of the basic glass that are represented by the palagonite of the tuffs, 

 we should look in vain. Basic or basaltic glass usually occurs in 

 agglomerates in the form of tachylytic pitchstones, as described on 

 page 312, and is also found at times in basic pumiceous tuffs, as 

 described on page 333; but it is far from frequent. Palagonite- 

 rock, that is to say, a basaltic glass converted in mass into this 

 substance, never came under my notice. 



In order to clear the ground for the discussion of my own observa- 

 tions, I will quote from the report on deep-sea deposits above named. 

 Fragments of basic glass undergoing the palagonite change are 

 found everywhere in these deposits and especially in the red-clay 



z 



