no. 2373. FERROANTHOPHYLLITE FROM IDAHO— SHANNON. 399 



CHEMICAL PROPERTIES. 



An analysis made upon selected fibrous material, which optical 

 study had shown to be pure, yielded the following results : 



Analysis offerroanthophyllilefrom Idaho. 



Silica (Si0 2 ) 49. 30 



Alumina (A1 2 3 ) 1. 30 



Ferric oxide (Fe 2 3 ) 2. 15 



Ferrous oxide (FeO) 30. 50 



Manganous oxide (MnO) 3. 48 



Lime (CaO) 10. 73 



Magnesia (MgO) 60 



Water (H 2 0) below 110° C 18 



Water (H 2 0) above 110° C 2. 13 



Total 100. 43 



The above analysis yields the following ratios: 



Ratios of ferroanthophyllite from Idaho. 

 Si0 2 0. 8170 8176 



A1 2 3 01271 2(J2 



Fe 2 3 0135/ 



FeO ! 4246' 



MnO 0491 



CaO 1913 > 7990 



MgO 0164 



H 2 1182. . 



For the sake of simplifying consideration of the ratios, the ferric 

 oxide and alumina may be deducted as the gedrite molecule, 

 RO.R 2 3 .Si0 2 ( X 262) , the ratios remaining after this deduction being: 



RO 7734 1X1. 00 



Si0 2 7914 1X1.02 



The formula thus derived for the mineral is : 

 (Fe,Ca,H 2 ,Mn)0. Si0 2 



or RSi0 3 with R = Mn :Ca :H 2 :Fe = 2:8:5:1 7 approximately. 



It will be noted that the water given off above 110° C. is here 

 included among the bases as an essential constituent, although present 

 views as to the occurrence of water in minerals hold that it is quite 

 possible for such an amount of water to be mechanically held through 

 adsorption by a mineral of this kind. In the present case the analy- 

 sis requires that the water be considered basic in order that the 

 composition of the mineral may be expressed as that of a normal 

 metasilicate. It seems more plausible here to regard the water as 

 constitutional than to reject it as extraneous and leave the analysis 

 with an excess of silica which can not be otherwise accounted for 

 Water is frequently considered to be a basic constituent of amphi- 

 boles. 



