1824.] M. Levy's Observations on the preceding Paper, 69 

 when one part of 8 A S is replaced by F S. Anorthite has only 

 been found hitherto in masses of carbonate of lime at Mount 

 Somma, near Vesuvius, where it is accompanied only by green 

 translucent pyroxene. , . v , , 



Observations. — The mineralogical formula indicated above, 

 appears to be the result of the analyses : I cannot, however, 

 warrant its exactness, because I could only operate upon very 

 small quantities ; the first time with 0-628 gr. ; the second time 

 with 1-482 gr. : it is the result of this last analysis I have given. 

 The formula would be analogous to other formulae already known, 

 if there was 9 A S, instead of 8 A S. Then it would be the 

 same as that of meionite and paranthine, the formula of which is 

 C S + 3 A S, with this difference, however, that one-third of 

 C S in anorthite would be replaced by M S. Anorthite would 

 then be referred to meionite, in the same manner as idocrase is 

 to garnet, or, according to my brother's analysis, pyroxene to 

 wollastonite. 



I have provisionally given the name of anorthite to this mine- 

 ral, derived from aoopfos, which signifies without right angles ; 

 because its crystalline form is principally distinguished from 

 felspar, in not being at right angles to each other. Haiiy, to 

 whom the name of felspar did not seem proper, had suggested 

 for this mineral the name of or those, from two of its cleavages 

 being at right angles to each other. 



Article XII. 



Observations on the preceding Paper, with an Account of a new 

 Mineral. By M. Levy, MA. of the Academy of Pans. 



(To the Editor of the Annals of Philosophy.) 



SIR Dec. 20, 1823. 



Since the notice you inserted in one of the preceding numbers 

 of the Annals of Philosophy of the division I had made of the 

 specimens commonly ranked under the name of felspar, into two 

 distinct species, viz. felspar and cleavelandite, I have seen in the 

 last number of the Aimales de Chimie a paper by M. Rose, of 

 Berlin, upon the same subject. An abstract of this paper is 

 inserted in the present number of the Atmals, and contains, in 

 addition to the essential part of what I intended to publish, not 

 only new analyses of both felspar and cleavelandite, and then- 

 specific gravities, but also the complete determination of two 

 new species, viz. labrador and anorthite. In consequence oi 

 this, I shall limit what 1 proposed to send you, to a very few 

 observations, which M. Rose's paper does not render useless. 



