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IX. On the Composition of Zeolite, By James Smithson, Esq . 
F.R.S. 
Read February 7, 1811. 
Mineral bodies being, in fact, native chemical preparations ? 
perfectly analogous to those of the laboratory of art, it is only 
by chemical means, that their species can be ascertained with 
any degree of certainty, especially under all the variations of 
mechanical state and intimate admixture with each other, to 
which they are subject. 
And accordingly, we see those methods which profess to 
supersede the necessity of chemistry in mineralogy, and to 
decide upon the species of it by other means than her’s, yet 
bringing an unavoidable tribute of homage to her superior 
powers, by turning to her for a solution of the difficulties 
which continually arise to them, and to obtain firm grounds 
to relinquish or adopt the conclusions to which the principles 
they employ, lead them. 
Zeolite and natrolite have been universally admitted to be 
species distinct from each other, from Mr. Klaproth having 
discovered a considerable quantity of soda and no lime, in the 
composition of the latter, while Mr. Vauquelin had not found 
any portion of either of the fixed alkalies, but a considerable 
one of lime, in his analysis of zeolite.* 
The natrolite has been lately met with under a regular 
* Journal des Mines, No. XLIV. 
