Prof. J. Emerson-Reynolds on Lievrite. 289 



These data, when discussed in the usual way, give the fol- 

 lowing ratios : — 



Si0 2 =-4983 = 3-85 =4-00, 



RO =-7431=5-74 = 5-96, 



R 2 3 =-1294=l-00 = l-04; 



or R 2 3 , 6RO, 4Si0 2 , 



where 6RO =4(Fe, Mn)0 + 2CaO nearly, neglecting the small 



amount of alkalies. 



As the water present in the particularly pure specimen of 

 the mineral analyzed did not reach 05 per cent., it is difficult 

 to admit, with Stadeler, that it enters into the molecule of 

 the compound; I therefore prefer to regard Lievrite as an 

 anhydrous silicate. 



Mr. Early's analysis of the mineral agrees in all essential 

 particulars with those of Rammelsberg and von Kobell, though 

 both those distinguished observers found slightly more iron in 

 the ferric condition. A comparison of the analyses of different 

 specimens of Lievrite by Rammelsberg, von Kobell, Stadeler*, 

 and Early prove that there is little variation in the proportion 

 of FeV to Fe" ; I am therefore disposed to regard the former 

 as an essential constituent of the mineral, rather than as a pro- 

 duct of the oxidation of a calcio-ferrous silicate. That the 

 mineral oxidizes in time there can be no doubt ; but I have 

 had a number of specimens of Lievrite under observation for 

 nearly ten years, and though two of them were placed in a 

 rather damp case, they suffered comparatively slight superficial 

 oxidation. 



If, then, we admit that Lievrite is essentially a dicalcic- 

 ferroso-ferric silicate, we can assign to it the following sym- 

 metrical formula: — 



Fe"f ,Si-O x O-SiT Fe" 



u 



6 



/°\V / \ Y/\ 



Fe // X x Si-0 X \0-Si; Fe" 



\/ x/ 



This formula has at least the merit of indicating that the 

 function of the ferric group is probably one of considerable 

 importance, and that, so far from being regarded as an acci- 

 dental constituent of the mineral, it ought to be considered 

 one of the most important components of the molecule of the 

 compound. 



* See Dana's ' System of Mineralogy,' 5th edition, p. 29G. 



Phil. Mag. S. 5. Yol. 3. No. 18. April 1877. U 



