280 Analysis of some Scottish Zeolites. 



Analysis of Scottish Zeolites. 



Pectolite. — The first of the series is a mineral which occurs 

 in the Island of Skye at Storr, which, in its external charac- 

 ters, bears a considerable resemblance to dysclasite, for which 

 I at first took it. It is met with in compact fibrous masses, 

 composed of radiated needles, of extremely minute size 

 and silky lustre. It is exceedingly tough, and breaks with 

 difficulty. Its specific gravity is 2 784. Before the blow- 

 pipe it fuses, without intumescence, into a bead, and also 

 gives slight indications of the presence of alumina and man- 

 ganese. 



On comparing it with an undoubted specimen of dysclasite, 

 however, it evidently presents a much higher lustre than that 

 mineral possesses, although in other respects there is but 

 little or no observable difference in the external appearance 

 of the two minerals. It is partially soluble in hydrochloric 

 acid, with the aid of heat, viscid flakes of silicic acid being 

 separated ; and in this particular it agrees with Von KobelPs 

 account of a specimen of pectolite from Monte Baldo, of 

 which he has published an analysis. On a qualitative exa- 

 mination, it was found to contain silica, lime, soda, alumina, 

 and water ; and its quantitative analysis was very simple, 

 the results being as follows : — Silicic acid, 52*007 ; alumina, 

 1-820; lime, 32-854; magnesia, 0396; soda, 7-670 ; water, 

 5058 = 99-805. If we exclude as unessential the small quan- 

 tities of alumina and magnesia found in this analysis, the 

 oxygen of the silicic acid, lime, soda, and water, is in the 

 ratio of 12 : 4 : 1 : 2, and would indicate that the mineral is a 

 compound of a neutral silicate of lime, with a basic silicate 

 of lime and water, giving for its formula, 



Na O Si 3 + (4 Ca O 3 Si 8 ) + 2 HO. 



The calculated results of this combination are, 



Silicic acid, 4 atoms, 181*2 - 52'6 



Lime, 4 ... 1120 - 32'4 



Soda, 1 ... 313 - 91 



Water, 2 ... 18- 5-9 



342-5 100-0 



