Chemical Co??iposition of Amphibole. 



27 



mode of formation of amphibole in nature that a brief outline 

 of von Chrustchoff's method may be given here to advantage. 

 In his experiment aqueous solutions of silica, alumina and 

 ferric hydroxide were taken, carefully prepared by dialysis, 

 freshly precipitated ferrous hydroxide, lime water, magnesium 

 hydroxide suspended in water and sodium and potassium 

 hydroxides ; these constituents when brought together made a 

 rather stiff gelatinous mass, which was placed in several glass 

 bombs (JBirne) : the bombs were then exhausted, hermetically 

 sealed, and continuously heated for a period of three months 

 at a temperature of 550° C. Several of the bombs exploded, 

 but three of them withstood the severe strain, and on opening 

 these there was found a brownish deposit containing well 

 formed crystals l mra long and J mm thick, of brilliant luster, 

 dark color and showing forms commonly observed on amphi- 

 bole ; h (010), m (110) and r (Oil). The prismatic angle could 

 only be measured approximately, but r^r', 011^011, gave 

 with exactness 31° 32', which is like one of the fundamental 

 amphibole angles of Koksharov. An analysis of the crystals 

 is here given and for comparison the results obtained by Stan- 

 ley from the black amphibole (hornblende) from Edenville, 

 N. Y. 



Sp. gi 



SiO, ... 

 TiO ... 





Artificial Cry 

 3-245 



stals 



I 16-02 

 ,24-44 



Edenville 

 3-284 





4235 



41-99 

 1-46 



Al O _. 





8*11 



11-62 ) 



FeO 





7-91 



2-67 ] 



FeO ... 

 MnO ... 

 MgO ... 



CaO ... 

 Na 2 .. 

 KO ... 





10-11 



14-33 



1321 



2-18 



1-87 



14-32 "J 

 0-25 V 



11-17 ) 



11-52 

 2-49 

 0-98 



H„0 (loss on i 

 (H„0 at 110°) 

 F . 



gnition) - 91 



0-53 

 0-08 

 0-80 











14-29 

 25-74 



100-98 



99-83 



The two analyses are very much alike, especially when it is 



"Le higher A1 2 3 and FeO of the 

 respectively by lower Fe 2 3 and 



taken into 'consideration, that the higher A1„0, and FeO of the 



Edenville material are offset 

 MgO. 



The failure to make amphibole by ordinary methods of 

 synthesis, and the success of von Chrustchoff's experiment 

 indicate clearly that the conditions necessary for the formation 

 of the mineral are those which are obtained with difficulty in 



