456 DR T. THOMSON'S Analysis of some Minerals. 



cimens have been found at Kilmacolm in Renfrewshire ; and I 

 am indebted to my friend and pupil Mr BROWN, for a very fine 

 collection of chabasites from that locality. It is in large trans- 

 parent rhomboidal crystals, constituting the well known primary 

 form of this mineral. Chabasite has been analyzed thrice by 

 BERZELIUS, and once by ARFWEDSON. The following table ex- 

 hibits the results of these analyses : 



Silica, .... 50.65 48.30 48.00 49.17 



Alumina, . . . 17.00 19.28 29.00 18.90 



Lime, .... 9.73 8.70 8.35 



Magnesia, . . 0.40 



Potash, .... 1.70 2.50 0.41 



Soda, 2.75 12.19 



Water, .... 19.50 20.00 19.30 19.73 



98.58* 98.78 f 99.21$ 99.99 

 o.i . 



The last analysis in the table was made by BERZELIUS upon 

 a specimen from Scotland. It is very remarkable, from the to- 

 tal absence of lime, which occurs as a constituent in every other 

 chabasite hitherto subjected to analysis. BERZELIUS informs us, 

 that under the soda a little potash is included. 



It was this last analysis that induced me to introduce chaba- 

 site into this paper. BERZELIUS has given no other locality ex- 

 cept Scotland. Nor has he favoured us with any description of 

 the mineral subjected to analysis ; both of which would have 

 been very desirable. That the chabasite of Scotland is not al- 

 ways composed, as BERZELIUS has found it in the specimen which 



* BERZELIUS ; Af hadl. vi. 190. The specimen was from Jutland. 



f ARFWEDSON ; Kong. Vet. Acad. Handl. 1824, p. 356. From Faroe. 



I BERZELIUS ; Ibid. The variety called Leveyne, and from Faroe. 



