a new Mineral Species. -^ ' ^ 'r 57 



lysis 17-515 : 34-990, and for the second 17-140 : 35-198. As 

 it appears from the third analysis that the amount of silica in 

 the second is rather too low, we may regard the first as ex- 

 pressing more exactly the ratio, which is just 1 : 2, and which 

 makes it a protosilicate in the nomenclature of M. Gerhardt, 

 pertaining to the type Si O^(M^) *. 



The composition is very closely expressed according to the 

 Berzelian notation by 5Si 0^ 12MgO, If AP 0^, ^Fe^ 0^ 12H0, 

 which may be represented among others by the formula 



2(AP 03 Fe^ 03), Si 03 + 4(3MgO, SiO^) + 12H0. * 



This affords by calculation the following numbers, which are 

 compared with the first of the analyses above given, from which 

 the carbonate of lime has been deducted : — 



Calculated. Found. 



Silica 33-29 32-84 



Magnesia .... 35-50 35*12 



Alumina .... 13-31 13-37 



Peroxide of iron . . 1-92 2-00 



Water 1600 1636 



100-02 99-69 



vj iThe peroxide of iron is to be regarded as replacing a portion 

 of the alumina, so that the mineral is essentially a hydrated sili- 

 cate of magnesia and alumina, which, denoting Alf by Al/9, will 

 in the notation of Gerhardt be represented by 



Si03(Al/8fMgfH|.). 



The only mineral hitherto described which approximates to 

 this in constitution is chlorite, which belongs to the same type, 

 and is represented* by Si 03(Al/8f Mg| H|) ; the principal dif- 

 ference in chemical composition being in the proportion of water. 

 The hardness and other physical characters of this mineral are, 

 however, such as to distinguish it completely from chlorite, and 

 seem to warrant its erection into a new species, for which I 

 propose the name of Loganite, in honour of the distinguished 

 geologist who is at the head of the Geological Commission of this 

 province. 



Montreal, C.E., Feb. 1,1851. 



* Introduction h V^tude de la Chimie par le Systeme Unitaire, par Ch. 

 Gerhardt, p. 349. He takes for the equivalent of siUcon 87"5 on the oxygen 

 scale, which will equal 262-5 if we regard silica as Si O^. It is this number 

 which I have used in the calculation of the analysis. M. Gerhardt repre- 

 sents silica by SiO, and hence the formula Si 0^(M^)=SiO, 2W 0, corre- 

 sponds in the Berzelian notation to SiO^, 6M0. , 01^)$% 



F2 



