Mineralo£rical Notices. 503 



o 



Vermiciilite is imbedded in a decomposed, magnesian, 

 probably steatitic mass, of a light mealy appearance ; from 

 this it is almost impossible completely to clear it. Thomp- 

 son, no doubt, therefore analyzed a considerable proportion of 

 this substance with his specimen of Vermiculite. Steatites 

 contain but a mere trace of alumina ; hence his analysis 

 would naturally "five much less of this inorredient than Herr- 

 man's of Pyrophyllite. Accordingly, we find, in Herrman, 

 29^ per cent alumina, in Thompson, only 1\ per cent. On 

 the other hand, steatite contains about 30 per cent, of mag- 

 nesia. And here the same coincidence takes place. Herr- 

 man finds only 4 per cent, magnesia, and Thompson 17 per 

 cent. They also differ about 5 per cent, in the quantity of 

 water. This is not surprising in a mineral whose singular 

 character in heat is supposed to arise from the mechanical 

 existence of water between the laminae, although I do not 

 consider it a fact by any means proved that it is water alone. 

 The ingredients of both analyses are the same, only differing 

 in quantity, except the iron, which, in one, is peroxide, in the 

 other protoxide. The difference in these two analyses, I con- 

 ceive far from being an objection to their identity. Among 

 the vermiculite, I have recently observed several laminae, of a 

 light apple-green color, resembling the original description of 

 Pyrophyllite by Herrman. Should future researches com- 

 pletely prove their identity, I believe Vermiculite was first 

 described. This name ought, therefore, properly to attach 

 to the mineral ; but this is a subject of very trivial im- 

 portance. 



In the future progress of geology, when the lines and 

 directions of paroxysmal action are better understood, a strict 

 comparison of the inorganic ingredients of the elevated 

 mountains and crystalline intrusions arising from periodical 

 movements or convulsions of the central liquid mass, in places 

 distant from each other, will certainly become a subject of 

 considerable interest, and be invested with a character some- 

 what resembling that of the comparison of the organic ingre- 

 dients of sedimentary deposits ; nor is it impossible that such 



