JS4f Intelligence and Miscellaneous Articles. 



Chesterfield, of a brilliant, transparent, dark ruby red. I name this 

 subject, because, as in the previous instance of pyrochlore, the small 

 transparent crystals of minerals are usually most free from adultera- 

 tion, and the fittest to produce the true atomic formula on chemical 

 analysis. The excellent observations of Rammelsberg on this whole 

 subject are well worth the attention of all mineralogists. 



Pyrophyllite and Vermiculite. 



In the paper before alluded to, published in the Proceedings of 

 this Society, I have stated the probability of the identity of these two 

 minerals. 



Vermiculite is imbedded in a decomposed, magnesian, probably 

 steatitic mass, of a light mealy appearance ; from this it is almost im- 

 possible completely to clear it. Thomson, no doubt, therefore ana- 

 lysed a considerable proportion of this substance with his specimen 

 of vermiculite. Steatite contains but a mere trace of alumina ; hence 

 his analysis would naturally give much less of this ingredient than 

 Herrman's of pyrophyllite. Accordingly we find in Herrman 29^ 

 per cent, alumina, in Thomson only T^ per cent. On the other 

 hand, steatite contains about 30 per cent, of magnesia. And here 

 the same coincidence takes place. Herrman finds only 4 per cent, 

 magnesia, and Thomson 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 as to heat is supposed to arise from the me- 

 chanical existence of water between the laminse, 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 conceive far from being an 

 objection to their identity. In vermiculite I have recently observed 

 several laminse of a light apple-green colour, agreeing with the ori- 

 ginal description of pyrophyllite by Herrman. Should future re- 

 searches completely 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 importance. 



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 cha- 

 racter somewhat resembling that of the comparison of the organic 

 ingredients of sedimentary deposits ; nor is it impossible that such in- 

 vestigations may eventually elicit data of great importance in geology. 



For the generalizations of some future master spirit on this sub- 

 ject, the mineralogist of the present day is storing up facts and ma- 

 terials ; and it is from this prospect that a discovery of the identity 

 of minerals from distant localities, and the purification of mineralogy 

 from the numerous supposed new species with which the conceit or 

 want of industry of its votaries have loaded it, becomes an object of 

 some interest. 



