48 Chemical Kxaminaiion of American Minerals. 



3 atoms silicate of alumina, 



1 atom silicate of peroxide of iron. 



But as it is not crj/stalized, we have no means at present 

 of determining what are its essential constituents. It will pro- 

 bably constitute a new species, being very different in its ap- 

 pearance from any mineral which I have hitherto had an op- 

 portunity of seeing. The brownish-black plates in some of 

 their characters, approach pinite; but the composition and 

 characters of the plumbago-looking portion, are very differ- 

 ent from all the other species of stony minerals that I have 

 seen. 



Note. Mr. Nuttall, with whom 1 have conferred respecting 

 the minerals which he sent to Dr. Thomson, is not altogether 

 certain that he recognises the substance called " phyllite." 

 The specimen examined in this analysis, was labelled in his 

 catalogue " titaniferous iron ;" and he informs me, that 

 the ore was imbedded in what he considered as a singular 

 ferruginous mica-slate. It is the latter substance which was 

 analyzed. The brownish-black micaceous scales noticed by 

 Dr. Thomson, are what Mr. Nuttall supposed to be an ore of 

 iron. 



15. HYDROUS SILICATE OF MAGNESIA. 



There seems no reason to doubt that the Swedish mineral 

 described in 1813, by Hanssmann, under the name of picro- 

 lite, is the same with the precious serpentine of Werner. The 

 external characters, as far as they have been given, are very 

 nearly the same ; and if we compare the analyses of these 

 minerals by Hisinger, Stromeyer and Almroth, we shall find 

 that they agree very closely, as may be seen by the following 

 table. 



