1824.] M, Rose on Felspar, Albite, Labrador, fyc. 49 



Article XI. 



On Felspar, Albite, Labrador, and Anorthite. 

 By M. Gustavus Rose.* 



Some differences I had found in the angles of crystals 

 described hitherto as felspar, induced me to examine them with 

 greater accuracy. From my observations, it results that four 

 different species, which differ as much in their form as in their 

 chemical composition, had been united under the common name 

 of felspar ; it is true that there is a great analogy in their crys- 

 talline forms. 



Among these species, that which will retain the name of 

 felspar, KS J + 3AS 3 , is the one met with most frequently. 

 Under that name must be classed the adularia from St. Gothard, 

 vitreous felspar from Vesuvius and from Siebengebirge, the 

 amazon-stone, the felspar from Friedrichwarn, in Norway, which 

 had been taken for labrador, the felspar from Baveno, from 

 Carlsbad, from Fichtelgebirge, and in general the greater part 

 of what Werner has called common felspar. 



The second species called albite (cleavelanditef) N S 3 + 3 A S* 

 is not so common as felspar. We are indebted to M. Eggerts 

 for the first notice of this substance; he examined a radiated 

 variety of it from Finbo and from Broddbo, near Fahlun. 

 Since, MM. Hausmann and Stromeyer have also found it in a 

 rock from Chesterfield in North America, and M. Hausmann 

 named it Kieselspath. M. Nordenskiold found the same sub- 

 stance in a granite from Kimito, near Pargas, in Finland ; and 

 lastly, M. Ficinus in a granite from Penig, in Saxony ; but all 

 these varieties were not regularly crystallized. The crystals of 

 the same substance which 1 have had an opportunity of seeing, are 

 the crystals from Dauphiny, which Rome de LTsle had described 

 under the name of schorls blancs, and which afterwards Haiiy 

 took for felspar ; the crystals from Salzbourg and the Tyrol, de- 

 scribed as adularia; the crystals from Kerabinsk in Siberia, 

 from Arendal in Norway, from Prudelberg near Stirschberg in 

 Silesia; as well as many other crystals from different localities. 

 The third species is the labrador (labrador-felspar) which 

 Klaproth had already analyzed and separated from felspar ; the 

 external characters of this substance had, however, prevented 

 mineralogists from making a distinct species of it. From the 



• Translated (with some omission*) from the Annales tie Chimie et de Physique, 

 tome xxiv. p. 5. 



UMIIC AtlVi p. J. 



* This name (cleavelandite) was proposed for albite by 3Jr. Brooke, but the origi- 

 nal term has been preserved in this translation. 



New Series, vol. vn. e 



