Analysis of some Scottish Zeolites. 283 



Silicic acid, 2 atoms = 92-444 = 4647 



Alumina, 1 ••• = 51-344 = 25*81 



Lime, 1 ... = 28-132 = 14-14 



Water, 3 ••• =27' = 13-58 

 



198-920 100- 



Several analyses of this mineral have been already pub- 

 lished, and are contained in the mineralogical works of Ra- 

 melsberg, Von Kobell, and others, on comparing which with 

 the results I obtained from the Mull specimen, they will be 

 found to agree generally with the whole of them, but most 

 closely with those of Giilich and Gibbs of the Iceland variety, 

 of Domeyko of the Cachapual specimen, and of Fuchs and 

 Gehlen of the mineral from Staffa and Faroe. 



Natrolite. — This mineral was found during the formation 

 of a railway tunnel near Bishoptown, Renfrewshire. The 

 specimen which I analysed was composed of beautiful needle- 

 shaped crystals, about two inches in length, of a pure white 

 colour and satiny lustre, interlaced into a felty mass. It 

 occurs in juxtaposition with another mineral, which was at 

 first supposed to be identical with it, consisting of long ra- 

 diated needles, with crystals of calcareous spar disseminated 

 here and there through them, and having a great resemblance 

 to the scolezite which I had previously analysed. A quanti- 

 tative analysis of this mineral has since proved it to be 

 Mesolite, or lime and soda mesotype. The three minerals 

 in question indeed seem to be isomorphous, and bear such a 

 resemblance to one another in their external character as to 

 render it exceedingly difficult, if not impossible, to distinguish 

 them from each other, without subjecting them to chemical 

 analysis. 



I found the specimen first mentioned to be entirely and 

 readily soluble in a solution of oxalic acid, at once proving 

 the absence of lime, a distinguishing characteristic of na- 

 trolite. 



Its quantitative analysis was as follows: Silicic acid, 47*626 ; 

 alumina, 27-170; soda, 15-124; water, 9-780 = 99-700, and 

 corresponds with the well-known formula of natrolite. 



Na O Si 3 + Al 2 3 , Si 3 + 2 HO. 



