MINERALOGICAL CHANGES OBSERVED IN CORES OF FUNAFUTI BORINGS. 4 lU 



Fig. 66. — Coral substance replaced by porous 

 massj of dolomite crystals; cavities filled with 

 fine calcareous detritus dolomitised. 



Fig. 67. — Coral substance converted into granular 

 calcite ; cavities containing water-clear calcite 

 in some cases, and in others first a layer of 

 transparent dolomite crystals, and then fibrous 

 encrusting material consisting of alternating 

 layers of calcite and dolomite. 



Fig. 68. — Originally coral with cavities partly 

 filled with fine calcareous detritus ; coral sub- 

 stance removed by solution ; cavities so formed, 

 and those incompletely filled with calcareous 

 detritus, lined with crystals of calcite, deposited 

 from solution, the whole then dolomitised, and, 

 lastly, fibrous encrusting calcite, deposited in 

 certain of the empty spaces. 



Fig. 69. — Originally coral with empty spaces; 

 coral substance removed by solution; cavities 

 so formed and the original cavities of the coral 

 lined with calcite crystals ; these converted 

 into dolomite ; and lastly remaining cavities 

 filled with fibrous encrusting deposit of calcite. 



3 H 2 



