191112 ] 



54i 



APPEARANCE. 



The characteristic appearance of beekite has already been 

 described. "Tubercles," "warts," globules and discs of chalce- 

 dony are surrounded by whorls, or to use Von Buch's happy 

 description, waves of the same mineral. A typical specimen of 

 Exogyra columba may be described. It consisted of a whole 

 valve of this fossil heavily beekised inside and outside. On 

 immersion in hydrochloric acid the interior of the valve, consisting 

 of unreplaced carbonate, was dissolved out leaving a cavity between 

 the two layers. The whorls or waves varied in number from 2 to 

 7 around the nuclear discs, and in one case 3 sets of 6 whorls 

 were surrounded by a common set of whorls seven in number, 

 having a total diameter of 1 cm. The whorls on the interior of 

 the shell bore no regular disposition towards those on the exterior. 

 The space between the exterior and interior contained stalactitic 

 masses of beekite of branching form, pointing roughly towards the 

 interior space. Occasionally these stalactites presented the ringed 

 form, in which case they appeared like little columns of buttons 

 growing smaller and smaller towards the interior of the cavity. 

 The total thickness of the beekised valve was 6 mm., and that of 

 the interior and exterior deposits of silica 1 to 1.5 mm. The 

 stalactites of beekite inside the cavity were composed of threads 

 and globules of chalcedony. The whole appearance suggested an 

 attacking force of a solvent solution, greatest on the interior and 

 exterior surfaces of the shell and diminishing gradually as it 

 worked its way into the shell material. In some cases the whorled 

 structure of the beekite was more evident on the interior of the 

 valves, suggesting a preponderance of organic matter on that side. 



COMPOSITION AND MICROSCOPICAL APPEARANCE. 



My chemical analyses gave very similar results to those of 

 Church, to which I can add but little. A typical specimen of 

 Exogyra columba beekite from the Chloritic Sands of Co. Antrim 

 gave Silica 97.32 per cent.; Lime 2.24; Aluminium and Iron 



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