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but in the third we difcern a beginning cry- 

 ftallization. One of thefe modifications 

 may be feen in the fixth fpecies ; and we 

 know that there are zeolites of other con- 

 figurations ; as fome with twenty-four facets, 

 and others with thirty. 



Some naturaUfts have affirmed that the 

 whiteft and pureft zeoHte of Ferro is the 

 only one from which a tranfparent and white 

 glafs can be obtained. I find, however, the 

 glafs of the fixth fpecies preferable to it ; 

 for it has an aqueous colour, and its tranf- 

 parencyis almoft equal to that of quartzofe 

 cryftal. I have found no zeolitic cryftals, 

 but thofe of the ifles of the Cyclops, which 

 have furnilhed a glafs equal to this. 



No mineralogifl: is ignorant that Cronftedt 

 was the firfl who diftinguifhed this ftone 

 from the carbonates of lime with which it 

 was confounded, and made us acquainted 

 with feveral of its qualities. He obferved 

 that mineral acids caufed no efFervefcence 

 with it, but flowly dilTclved it into a gela- 

 tinous 



