144 



The dispersion is thus rather considerable and takes place 

 according to the formula 



p >v. 



The specific gravity of leucosphenite has been determined 

 by weighing in benzole and found to be 3,05 (Mauzelius). Its 

 hardness is 6,5. The mineral has a distinct cleavage parallel 

 to the second pinacoid b {OIOJ. The mineral is often easily 

 cleaved in this direction; but in sections cut perpendicular to 

 the cleavage, this is seldom quite distinct. A cleavage parallel 

 to the form n could not be detected, though the mineral often 

 shows a pearly lustre on the faces of this form. 



As the material available was very scanty, no more than 



0,5238 gr. of pure substance could be procured for the analysis. 



The analysis has been made by R. Mauzelius; and the values 



obtained are as follows. 



Molecular ratios 

 SiO^ 56,94 0,943 10 



2,06 



TiO., ......... 13,20 0,165 I 



ZrOo 3,50 0,025 / " 



BaO 13,75 0,090 0,95 



Na.^0 11,14 0,180 I 



K^O 0,56 0,006 j 



H.O 0,31 



1,97 



99,40 



To obtain an acceptable proportion between the acid and 

 the basic constituents, TiO^ and ZrO.^ must be made basic. 

 The formula then becomes 



BaO •2Na,,0-2Ti (Zr) 0,, • \0SiO., or 



BaNa^[TiO).,{Si^^Orj5. 



Leucosphenite would thus be a dimetasilicate , and the 

 only known substance of analogous composition would be peta- 

 lilc. The leucosphenite crystals do, indeed, remind one in some 



