Notes on Canadian Minerals. 95 



of air bubbles took place, the true specific gravitj' proved to 

 be 2-5H. 



On drying in vacuo over sulphuric acid the mineral lost 

 1*584 per cent, of its weight, but further drying in the 

 steam-bath gave an additional loss of only - 08 per cent. 

 Under I is given the analysis of the undried material, and 

 under II. the analysis calculated for the dried material : — 



I. II. 



Silica 42-42 43-13 



Magnesia 41-36 42-05 



Ferrous Oxide 0-36 0"37 



Manganous Oxide tr. tr. 



MckelOxide 1 » " " 



Lime •• " " 



Water 15-29 13-88 



99-43 99-43 



It will be seen that the substance has essentially the com- 

 position of serpentine, the figures for the dried material 

 coming very near to those required by the formula 

 Mg 3 Si 2 7 +2H 2 (Silica 43-48, Magnesia 43-48, water 13'04.) 

 The proportion of iron is much lower than that commonly 

 met with in serpentine, and in fact of the 78 analyses given in 

 Dana, there are only two showing as small a quantity. As 

 a rule, the serpentine rocks of the Eastern Townships con- 

 tain a considerable proportion of iron, and this we should 

 expect if we regard them as alteration products of basic 

 eruptive rocks. In the veins under consideration, how- 

 ever, we have serpentine of later origin, deposited by 

 aqueous agencies, and presenting, as might be expected, 

 striking differences from the parent rock, both in appear- 

 ance and composition. Such differences of origin are too 

 frequently lost sight of in the study of serpentines. 



The mineral described above resembles in some respects 

 such varieties of serpentine as retinalite and porcellophite. 



1 The presence of nickel was ascertained with the blowpipe, and 

 no attempt was made to estimate the quantity. 



