10 Bulletin op the New York State Museum. 



inclusions. With the exception of muscovite and quartz inclusions 

 and the fact that the mineral occurs in granular limestones. Rosen- 

 busch's description is quite applicable to this mineral. Since there is 

 no way of distinguishing wernerite from dipyre, save by chemical 

 analysis, a quantitative silica determination was made. The average 

 percentage of silica was 57.20. Since the percentage in wernerite 

 ranges from 44 to 48 per cent, and in dipyre from 55 to 60 percent ; 

 and, since both Hussak and Rosenbusch agree that r utile is a rare 

 inclusion in wernerite, I think the mineral may safely be called dipyre. 



II.-CALCITES FROM ROSSIE, ST. LAWRENCE COUNTY.* 



The calcites from Rossie, N. Y., collected by Prof. E. Emmons, 

 deserve special mention. They were taken from the Coal Hill and ad- 

 joining lead mines in the town of Rossie, St. Lawrence county. 

 The mine was opened about 1836, but was operated at a loss, and was 

 abandoned a few years later. During the process of working, how- 

 ever, some of the finest calcites in the world were obtained. Of 

 these, the Museum has, probably, the finest and most extensive col- 

 lection extant. All the different forms figured by Prof. Beck in his 

 " Mineralogy of New York," and by Prof. J. D. Dana in his " Sys- 

 tem of Mineralogy," with a few exceptions, are represented. 



There are no unmodified rhombohedra, and it is quite probable 

 that none were found. Scalenohedra of the simple type are not 

 common. Every crystal, without exception, is twinned, some of the 

 twins being very complex. The descriptions given by Prof. Beck, 

 will be found on page 224, "Mineralogy of New York" The twins 

 found at Rossie are usually parallel to the O-face. Sometimes the 

 O -plane is present on one of the crystals and not on the other, 

 sometimes on both, and then on neither. 1 It frequently happens 

 that when two crystals are thus twinned only three of the R-planes of 

 each crystal are present, while the O-planes are developed to such an 

 extent that the crystals appear in the form of a thick, triangular 

 crystal with bevelled edges, or rather, in the form of a* truncated 

 triangular pyramid. 2 



In another form two crystals are twinned parallel to i. and to a third 

 crystal parallel to the O-face. 3 On two crystals the O-face is developed, 

 on the third it is lacking. Not rarely crystals are found with from 



* Collection made by the late Prof. E. Emmons, of Williams College, about 1838, at the Kossie 

 lead mines. 



1 For references see plate at the end of Bulletin. 



2 see fig. V. 



3 This lorm is a combination of fig. Ill with one of the twinned crystals of flg. V. 



