456 Prof. B. Silliman on some American Minerals. 



light, but does not fuse, unless with great difficulty, on the 

 edges. It contains a trace of fluorine, and a qualitative ana- 

 lysis detected in it silica, alumina, lime, soda and water. An 

 insufficient quantity of the mineral prevented a perfect ana- 

 lysis being made. So far as its constituents have been ob- 

 tained, it contains, — silica, 36-369 ; alumina, 42-373 ; lime, 

 10141; magnesia, 4*462; water, 1-448; the difference, soda 

 and loss. Soda, about 4 per cent. '--^-^ 



Should it appear, on repeating the analysis of this mineral, 

 that it is new, as the present would appear to indicate, I would 

 propose to adopt the name Clingmanite, suggested by Prof. 

 Shepard, in honour of the distinguished gentleman before 

 named, who has shown great interest in advancing the study 

 of mineralogy*. 



I have had no means of comparing the optical properties 

 of these several minerals. The angle between their axes of 

 polarization should be measured to ascertain if the differences 

 shown in their composition are found also in their molecular 

 structure. When we review the characters of the minerals 

 here described, we are struck with the almost identity of all 

 their ordinary physical characters ; and yet there are differ- 

 ences which are apparent, especially in their composition. It 

 therefore becomes an interesting question, to decide if the 

 optical characters will sustain the chemical results. The oc- 

 currence of a class of salts with such a very small amount of 

 protoxide bases, and so large a quantity of alumina as these 

 possess, is a novelty in the chemical history of minerals, and 

 may have some important theoretical connexions. Our know- 

 ledge of the whole mica family is quite imperfect at present. 

 The true function of the fluorine found in so many of them 

 yet remains to be explained ; and especially is it of the great- 

 est importance that a careful series of optical measurements 

 should be made on authentic specimens from numerous locali- 

 ties, and at the same time an exact series of chemical analyses 

 conducted on specimens from the same localities. 



Mineralogy hardly offers a more inviting investigation than 

 this; and should it not fall into better hands, it will at a future 

 day be attempted in this laboratory. 



* ^l^^i ^' ^' ^'^^P^''^ had noticed this mineral, and supposing it to be 

 new, he had determined to give it the above name. When he found, how- 

 ever, that I was engaged on this series of minerals, he promptly abandoned 

 the investigation. At that time we both thought that the emerylite of 

 Dr. Smith would probably include all the American species herein described, 

 which now appears not to be the fact. On going to England in June, Prof, 

 bhepard left me a memorandum containing his notes on the North Caro- 

 iiiia mineral, and I have embodied them in the above description with inv 



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