464 Prof. B. Silliman o« some American Minerals, 



This analysis must certainly refer to another mineral than 

 boltonite. The description certainly does not compare at all 

 with that of boltonite, which cannot be said to "consist of a 

 series of prismatic crystals," with a glassy lustre and faint 

 green colour. Nor is it white. In searching among the 

 minerals from Bolton, in the cabinet of Baron Lederer, for 

 something corresponding with Thomson's description, I found 

 one from that locality marked " Picrosmine? " " Actynolite ?" 

 This mineral answers the description of Thomson, quoted 

 above, as nearly as anything could ; and is undoubtedly the 

 same thing which he received from Mr. NuttalJ, and examined 

 with the above results. Nothing else occurs at the locality at 

 all resembling the mineral which is described by Dr. Thomson. 

 A qualitative analysis of this specimen gave silica, magnesia, 

 alumina, peroxide of iron, manganese, but no lime or water. 

 These are the constituents of a hornblende, and this specimen 

 is undoubtedly such — variety actinolite*. 



If the foregoing conclusions are correct, it would appear 

 that boltonite and " bisilicate of magnesia " are not the same 

 mineral as described by Prof. Shepard. 



The formula for boltonite is that of a salt not before de- 

 scribed, while that deducible from Thomson's analysis, cor- 

 responds as accurately as we could expect with common 

 hornblende. 



I am happy therefore to be able to re-establish boltonite as 

 a species on good grounds. 



VI. On Nuttallite. 



Nuttallite was established as a species by Mr. Brooke t> on 

 general physical grounds, principally of hardness and colour, 

 and a slight departure from the usual angles of scapolite. It 

 was analysed by Thomson J, who found for it a constitution 

 so different from scapolite, that it has been regarded as a di- 

 stinct species by many mineralogists, and is so placed by 

 Nicol in his Manual just published. I was induced to make 

 a new analysis to decide the doubt regarding its true constitu- 

 tion. The mineral is partially decomposed by strong hydro- 



* I am altogether at a loss to understand what Dr. Thomson intends, 

 when he says in his memoir before quoted, that the analysis here given 

 corresponds to the constitution of a " bisilicate of magnesia.'' For 

 2 atoms SiO' = 92-52 = percent. 8172 

 1 atom MgO = 20-70 18-28 



113-22 100-00 



This result is entirely different from his analysis, 

 t Ann, of Philos., xli. p. 366. 

 i New York Lyceum of Natural History, vol. iii. p. 82. 



