1824.] Albite, Labrador, and Anorthite. 55 



Albite offers, however, sometimes crystals which are grouped in 

 a manner analogous to the hemitrope crystals of felspar. They 

 are joined to each other by their planes M, and consequently 

 have their planes P on different sides ; but in this case the two 

 crystals are attached by their other faces to other crystals in the 

 common way ; so that the whole is only an hemitrope formed 

 by two different hemitropes which are grouped in the same 

 manner as the two simple crystals which form the hemitrope 

 crystals of felspar of Carlsbad. 



Although albite is found massive, it is always radiated, never 

 in laminae, and that distinguishes it essentially from felspar. 

 It may always be admitted, therefore, that the felspar which is 

 met in this state is not felspar, but albite. The palmed felspar 

 of Johann Georgenstadt in Saxony, distinguished by Werner, is 

 among those of this kind the most known in Germany : how- 

 ever, some doubts may be entertained concerning several speci- 

 mens of various localities contained in the collection of minerals 

 at Berlin. 



Besides the albite of Arendal, I have analyzed thatofSalz- 

 bourg. Some circumstances have prevented me terminating the 

 analysis of it ; however, I have obtained soda, and the same 

 quantity of silex, as in the analysis of the albite of Arendal. 



The sulphate I had obtained, and which I had crystallized 

 with a great deal of care, gave me crystals perfectly similar to 

 those of sulphate of soda. When exposed to the atmosphere, 

 they fall to powder, and treated by the solution of platina, by 

 tartaric acid, and by sulphate of alumina, they exhibited the 

 same properties as sulphate of soda. Having mixed a solution 

 of these crystals with a solution of chloride of platinum in alco- 

 hol, it remained perfectly limpid, and evaporated to dryness, and 

 left a mass perfectly soluble in alcohol. A solution of these 

 crystals into which I had put tartaric acid, retained its 

 limpidity. In mixing this with sulphate of alumina and alcohol, 

 I obtained regular octohedrons perfectly well crystallized, which 

 I consider as sulphate of alumina and soda ; because when 

 opposed to the atmosphere, they were reduced to a fine powder, 

 and are thus sufficiently distinguished of sulphate of alumina and 

 potash, which mixed with alcohol was immediately precipitated 

 in a state of powder. 



In analyzing albite with carbonate of barytes, I have found a 

 loss of 2-}r per cent. It is undoubtedly soda which suffers this loss ; 

 this appears to me so much the more likely, for I obtained silex 

 and alumina in the same proportions as in analyzing albite with 

 carbonate of potash, and the result was the same in calcu- 

 lating the proportion of these two bodies from the same chemical 

 formula. I could not repeat the analysis, because 1 had used 

 all 1 had of the substance to determine the nature of the alkali 

 contained in albite, and for the analysis with the carbonate of 

 potash. 



