1824.] Albite, Labrador, and Anorthite. 53 



when two crystals are so joined to each other that the upper plane 

 of the one is applied upon the inferior plane P' of the other, in 

 the manner exhibited by fig. 3. The two crystals have Gene- 

 rally the same size -however all the differences which are known 

 to occur in the hemitropes are also met with in this substance ; 

 frequently one of the crystals is only visible by a narrow line on 

 the plane P of the other. A third crystal is often applied on the 

 second; and a fourth upon the third, &c. The hemitropes 

 attached to the matrix present always the same end upwards, 

 and that corresponds to the upper part of fig. o. 



This substance can be cleaved parallel to every plane of the 

 primitive ; the cleavage parallel to P is the most brilliant. The 

 colour of the crystals is white or reddish-white ; the crystals are 

 translucent or transparent, either wholly or in part as in those of 

 Kerabinsk. 



The specific gravity will be found in the following table : 



The specific gravity has been found before by 



Eggertz, that of Finbo 2*612 



Eggertz, that of Broddbo 2-619 



Nordenskiold, that of the red albite 



from Kimito 2-609 



Ficinus, that of the albite of Penig. . . 2-50 



The result of an analysis of crystallized albite from Arendal, 

 decomposed by means of carbonate of potash, is 



Silica 68-46 which contains oxygen 34-43^ 12 



Alumina 19-30 9-01 3 



Lime 0-68 



Oxide of iron 0-28 



Magnesia 



Loss 1 1-27 taken as soda 2-88 



Another analysis in which I had precipitated the alumina with 

 carbonate of potash, gave the following result: 



Silex G8-60 



Alumina, with a little oxide of iron. . . 19-25 



An analysis with carbonate off barytes, gave 



