Peach-Blossom Coloured Mica, 203 



veral species of mica ; but it appears clearly, from the experi- 

 ments of MM. IL Rose and Vauquelin, that, in so far as respects 

 the quantity of the oxide of titanium, this chemist is quite in 

 the wrong. As Mr Vauquelin, however, has himself discovered 

 in several specimens of mica, which he recently subjected to 

 analysis, traces of titanium, I did not omit to examine whether 

 or not this Mica also contains titanium. I followed exactly the 

 method proposed by Mr Vauquelin, * which is certainly well 

 fitted to discover the smallest traces of this metal in a mineral, 

 but I was not able to detect unequivocal traces of it. Muru 

 atic acid, which was boiled with the silica, separated by evapora- 

 tion in a water bath, had taken up nothing but a little chloride 

 of silver, (derived from the crucible in which the mineral had 

 been ignited with potash,) which was thrown down by water ; 

 and by adding afterwards an infusion of galls, no fusible pre- 

 cipitate fell down. The chloride of silver, somewhat colour- 

 ed, was, however, collected and examined before the blow-pipe 

 with salt of phosphorus. There was obtained metallic silver ; 

 but the glass assumed, even after the addition of tin, such an 

 undecided reddish hue, that the reaction could not be consi- 

 dered as a decided one. The other ingredients of this Mica 

 contained no trace of titanium. 



With respect to the lithion, which Mr Peschier conceives 

 he has discovered in a species of mica, it appears not impro- 

 bable that this chemist has likewise been deceived, and that he 

 has considered to be lithion what is really magnesia. His ex, 

 periments, at least, by no means prove the presence of lithion, 

 but rather of magnesia. I tried several pieces of mica before 

 the blow-pipe, but could not discover this alkali, not even in a 

 rose-red mica from North America, for which I am indebted 

 to my friend, Mr Brooke. 



It is evident, that the Mica from Chursdorf is nothing else 

 but a largely lamellated Lepidolite ; and it might, therefore, be 

 more adequate to distinguish the micas that contain lithion to- 

 gether with potash, from those which contain no lithion, by 

 the name of lithion-mica. It appears, besides, that potash is 

 as essential an ingredient of Lepidolite as lithion, and that Le- 



* Annates dc Chimic et dc Physique, par MM. Gay-Lussac et Arago, 

 t. xxvii. p. 67. 



