OBSERVATIONS ON THE TREMOLITE. 291 



Compofition only by infulated rays, or by combination of two 



or more, and not the whole of the rays ? We are, however, The phofphoric 



enabled to make an obfervation with refpea to this fubjeft, ^° e u [ n Fs al f ft e one9 



namely, that thefe ftones conftantly exhibit by the action of f the fame fpe- 



heat, a phofphorefcence of the fame colour, whatever may be *[ es > however 

 , r v in themfelvei may 



the colour of their proper fubftance. For inftance, the fluates be coloured. 



of lime which exhibit the moft lively and variegated colours, 

 conftantly give a light inclining to the violet, with the -tingle 

 exception of the Siberian variety, which has been named the 

 Chlorophane, and which, though of a violet colour, gives a 

 phofphorefcence of a beautiful emerald green. In others, as 

 in Ibme carbonates of fime, in thofe of barytes, of ftrontian, 

 &c. though thefe ftones are perfectly colourlefs, the phof- 

 phorefcence is conftantly reddifh, or orange yellow. What 

 may be the caufe of thefe contrafts ? 



In fome cafes the caufe which produces the phofphorefcence It may arjfe 

 of the ftones feems to belong to an efleniial part of their fub- from a P erma - 



o r \ tm • nent cau * c > or 



itance, which is never completely expelled from them. This from fome por- 



is the cafe with the calcareous fluates and phofphatea, &c. tl ™ tha * can be 



. • , n ■> abftra&ed. 



In others it appears to be purely accidental in the ltone, and 



thews itfelf only in a certain number of individuals belonging 



to the fame fpecies. In the firft cafe, this property ouglit to 



be indicated amongft the fpecific characters of the ftone ; in 



the fecond, it cannot ferve as character of the fpecies, but can 



merely be ufed to designate one of its varieties. Such is, for 



example, that which exifts in the tremolite and in the dolomie, 



refpecting which I intend here to offer fome obfervations, 



which appear to me to deferve the attention of mineralogifts. 



M. de Sauffure and Profeilbr Blumenbach were, as far as I The tremolite is 



know, the firft who obferved the two kinds of phofphoref- notin fJG* - 



. r mens pholpho- 



cence in the tremolite ; and, fince them, all the works of mi- refcent. 

 neralogy have placed this property amongft the distinctive cha- 

 racters of this ftone. Many tremolites, indeed, are endowed 

 with this double phofphorefcence ; but this is by no means the 

 cafe with all, nor can this character, be confidered as efiential 

 to its nature. 



The tremolite, both that which is found in different vallies Thofe which are 

 of Mount St. Gothard, and that which is brought to us from a 5n a phofphoref- 



, c . . .7; irj- cent gangue are 



great number ot other places, is generally mcloled in a granu- themfelves phof- 

 laled carbonate of lime, the grains of which are of various de- phorefc » ; and 

 grees of finenefs, and their adhefion more or lefs confiderable. ^hen the gangue 



U 2 Among is not phofpho- 



