180 Dr. Heddle's Analysis of the Mineral " Edingtonite" 



which gives the formula — 



3(BaO, Si O 3 ) + 4(A1 2 O 3 , Si O 3 ) + 12HO, 

 the calculated per-centages of which are, — 



Atoms. Per cent. 



In another analysis I got -08 of strontia (?) and -22 of lime. 



For the sake of comparison, Dr. Turner's analysis is appended 

 in a foot note* ; it will be observed that the lime and loss taken 

 together approximate the quantity of baryta obtained in the new 

 analysis. 



I would account for Dr. Turner's mistaking baryta for lime, 

 and also so far for the loss sustained, by supposing that, from 

 having merely a few chips of the mineral, he was unable to 

 institute a preliminary qualitative analysis ; and that he (under 

 the impression that, like most zeolites, it would be found to con- 

 tain lime) added oxalate of ammonia, and so got the partially 

 soluble oxalate of baryta, which in the washing passed to a great 

 extent through the niter, and if it was again noticed, was set 

 down as " probably potash or soda." I would explain the mis- 

 take thus, because I believe, not only that Dr. Turner was a most 

 correct analyst, but that he never willingly shirked any of the 

 intricacies; at the sametime a readier explanation might be offered 

 in the fact, that at this time baryta was often taken for lime. 

 Dr. Thomson, for instance, was detected by Connel mistaking 

 baryta and strontia for lime in Brewsterite, and by Damour in a 

 similar mistake with regard to " Morvenite." 



In virtue of its composition, as above stated, Edingtonite will 

 take a most interesting place in the system, ranking with har- 

 motome and Brewsterite as the third barytic zeolite ; thus 



Brewsterite (BaO, SrO) Si0 3 + Al 2 3 , 3Si 3 + 5HO. 

 Edingtonite 3(BaO, Si O 3 ) + 4(A1 2 O 3 , Si O 3 ) + 12HO. 

 Harmotome 3BaO, 2Si O 3 + 4(A1 2 O 3 , 2Si 3 ) + 18HO. 



The original specimen of this mineral was stated to have 

 occurred in cavities of Thomsonite. I have never seen it thus 

 associated. 



Before leaving Edingtonite, we would venture to throw out the 



* By Turner : — 



