38 



to the c-axis of the crystaP). Though the mineral transmits 

 but little light, the indices of refraction could be determined 

 with great accuracy. From the values of angles that were ob- 

 tained the following figures are calculated 





Green 



Yellow 



Red 



a) 



1,6767 



1 ,6742 



1,6718 



e 



1,7729 



1,7701 



1,7664 



—CO 



0,0962 



0,0959 



0,0946. 



For the parisite from Muso the indices of refraction have 

 been determined by Sen arm ont, whose values are quoted by 

 Des Cloizeaux. These values are as follows 



u) г e — a» 



1,569 1,670 0,10]. 



The Greenland mineral consequently has a considerably 

 stronger refraction than the American mineral. The strength 

 of the double refraction, on the other hand, is about the same 

 in the two minerals. 



Before the blowpipe in the forceps the mineral is infus- 

 ible and emits an intense white light. Splinters that have been 

 ignited are of a light liver-brown colour and traversed by 

 cracks. The mineral is fairly easily soluble in acids, with the 

 evolution of carbon dioxide. 



Of the analysis made by me the following account may be 

 given. Pure material for analysis has by no means been 

 wanting, and the values obtained could therefore be verified by 

 duplicate determinations. Both the carbon dioxide and the 

 fluorine were determined directly. The carbon dioxide was 



') All prisms and plates cut for the axial angle determinations, and micro- 

 scopical preparations used in this investigation have been made by Mr. 

 A. R. Andersson, «Preparator» at the Geological Institution of the 

 university of Upsala, with his well-known skill and care. They are 

 deposited, together with the rest of the material of investigation, in the 

 Mineralogical Museum of Copenhagen. 



