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fteel. It (hews no indication of having 

 fufFered by the fulphureous acids. It is full 

 of fmall long cavities, all in one diredtion, 

 and which probably were produced when 

 the lava was in a fluid flate. It is in thefe 

 cavities that this fpecies of zeclite is found. 

 At firft view it appears rather tobe a ftalac- 

 dcal calcedony, having the form of aclufter 

 of grapes. It is of a white pearl colour, 

 inclining to a light blue, and gives fome 

 fparks with fteel. It has a filiceous fradlure, 

 and a degree of tranfparency. Three pro- 

 perties, however, efpecially charadterife it ; 

 iirfl, that it forms a jelly with mineral acids; 

 fecondly, that it flaflies or blazes at the mg- 

 ment of fufion ; and, thirdly, that it bub- 

 bles, and as it were boils, when in fudon: 

 and though neither of thefe charaders ex- 

 clufively appertain to the zeolite, all the 

 three together fufficiently fix the nature of 

 this ftone, which muft be referred to the 

 clafs of amorphous zeolites. The clufter- 

 ing grains may be extraded entire, as they 

 attach to the lava but in a few points. The 

 largeft extend to five lines in length, by two 



or 



