Prof. B. Sittiman, Jr., on some American Minerals. 393 



resemblance to the picrosmine of Haidinger, both in character and 

 composition, " that he strongly suspects the two things to be mere 

 varieties.- The mineral is white, with a shade of green, powder 

 white. It consists of a congeries of prismatic crystals, very ir- 

 regularly disposed, and involved in each other. Lustre glassy ; 



transparent on the edges." The analysis gave : 



Silica, 

 Magnesia, 

 Alumina, 

 Perox. iron, 



56-64 

 36-52 



607 

 2-46 



101-69 



This analysis must certainly refer to another mineral than Bol- 

 tonite. 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 color. 

 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 de- 

 scription of Thomson, quoted above, as nearly as anything could, 

 and is undoubtedly the same thing which he received from Mr. 

 Nutlall, and examined with the above results. Nothing else oc- 

 curs at the locality at all resembling the mineral which is descri- 

 bed by Dr. Thomson. A qualitative analysis of this specimen 

 gave silica, magnesia, alumina, peroxyd 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 described, 

 while that deducible from Thomson's analysis, corresponds as 

 accurately as we could expect with common hornblende. 



I am happy therefore to be able to reestablish Boltonite as a 

 species on good grounds. 



Thomson 



in his memoir before quoted, that the analysis here given oorreeponde to the consti- 

 tution of a "Bisilicate of magnesia." For 



magn 



% atoms Si = 91252 = per ct 81V2 



1 atom Mg = 20-70 18 ' 28 



113 22 100*00 



This result is entirely different from his analyst 



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