294 



S. L. Penjield — Minerals from Italy , etc. 



all corresponding closely in their angles to pyroxene. He also 

 presents an analysis by Damonr which, as the material was 

 impure from the presence of a fibrous mineral supposed to be 

 tremolite, he regards as only approximate. Later* he showed 

 that the optical properties were like those of diopside and pre- 

 sented an additional analysis by Pisani. A chemical analysis 

 has also been made by Schluttig.f The analyses, all of which 

 are given on page 357 of the sixth edition of Dana's System 

 of Mineralogy, show considerable variation and do not yield a 

 satisfactory formula. 



In studying out the relations of the light colored pyroxene 

 associated with alurgite, to the other members of the pyroxene 

 family, it seemed to show a similarity to violan, especially as 

 the analyses showed that they were both rich in soda and con- 

 tained manganese and sesquioxides. As there was an excel- 

 lent specimen of violan in the collection of Prof. Brush it 

 seemed best to make a new analysis of it. The material was 

 selected by hand and after crushing and sifting to a uniform 

 grain it was separated by means of barium mercuric iodide 

 solution. The portion that was taken for analysis varied in 

 specific gravity between the limits 3*272 and 3*237. As given 

 by other authors it varies from 3*21 to 3*233. The material 

 when examined under the microscope was apparently very 

 pure. The color was a beautiful light blue. The analysis is 

 as follows : 







Ratio 



Si0 2 



_. 53*94 



•899 



A1 2 3 -- 

 Fe 2 3 ... 

 Mn 2 3 ._. 



.. 1*00 



•86 

 •88 



•010 

 •005 

 •006 



MnO____ 

 MgO.... 



CaO .... 



•36 

 _. 16*63 

 .. 23-80 



•005 

 •416 

 •425 



Na 2 ... 

 Ign 



.. 1*22 



•05 

 •66 



•020 

 •001 





99-40 





•021 



•846 



•021 



NaR(Si0 3 ) 2 

 •084 



•021 



CaMg(Si0 3 ) 2 

 •815 



•846 



•021 



These results differ from those of other investigators in 

 showing less alkalies and sesquioxides. Moreover the identity 

 which Igelstrom"): has sought to establish between violan and 

 the mineral from Jakobsberg, Wermland, described by him§ 



* Manual de Mineralogie, vol. ii, 1874, p. xix. 



flnaug. Diss. Leipzig, 1884. Zeitschr. Kryst., vol. xiii, p. 74. 



% Jahrb. I Min., 1890, 2, p. 270. § Jahrb. f. Min., 1889, 2, p. 36. 



