Intelligence and Miscellaneous Articles. 153 



have not come from any distance. Its other leading external cha- 

 racters, including transparency and colour, agree with those of pre- 

 cious garnet and pyrope, the colour approaching the deeper tint of 

 the latter; its specific gravity is 3*661. 



Twenty grains of this mineral in very fine powder, were fused 

 with four times their weight of carbonate of potash ; the mass was 

 treated with muriatic acid, and no smell of chlorine observed. Si- 

 lica was separated by the usual method ; the precipitate obtained 

 by ammonia was dissolved in muriatic acid, the solution boiled 

 with excess of potash which took up the alumina, and the matter 

 left by this alkali was dissolved in muriatic acid ; to this solution 

 tartaric acid and ammonia in excess were added, and a current of 

 sulphuretted hydrogen, passed into it, threw down sulphuret of 

 iron with a little sulphuret of manganese. The filtered liquid was 

 evaporated to dryness, and the residue incinerated was pure white ; 

 it was carefully examined for yttria, which Dr. Apjohn, some few 

 years ago, announced that he discovered in pyrope. This white 

 matter was dissolved in muriatic acid, and muriate of ammonia and 

 excess of ammonia were added ; a gelatinous precipitate fell, which 

 by ignition acquired a greenish-yellow tint, and magnesia was left 

 in solution. The ignited precipitate was again dissolved in muriatic 

 acid, and yielded a gelatinous precipitate by treatment with am- 

 monia and its muriate ; this was dissolved to a great extent by 

 potash, leaving a substance which was principally oxide of iron, but 

 gave a permanent fine, though pale emerald- green colour to salt of 

 phosphorus, and therefore contained a trace of oxide of chromium. 

 It was determined by a separate experiment that the iron contained 

 in the mineral was entirely in the state of peroxide. 



One hundred parts of this substance were found to consist of 



Silica 42-80 



Alumina 28*65 



Peroxide of iron 9'31 



Protoxide of manganese 025 



Lime 478 



Magnesia 10-67 



Oxide of chromium, trace 



96-46 



The deficiency Prof. Connell conceives to be probably owing to 

 some magnesia which might have escaped precipitation by the car- 

 bonate of potash. 



Prof. Connell remarks, that even if the oxide of iron in this mi- 

 neral were held to be protoxide (instead of peroxide, as he found it), 

 there would be quite as much difficulty in bringing the result under 

 the garnet formula as there is in bringing the leading analyses of 

 Bohemian pyrope under it. This circumstance, as well as the ge- 

 neral conformity between the above result and the analyses of pyrope, 

 comprising those of Klaproth, Wachtmeister and Von Kobell, par- 

 ticularly as respects the considerable quantity of magnesia and the 

 comparatively small quantity of oxide of iron, notwithstanding the 



Phil. Mag. S. 3. Vol. 27. No. 183. Feb. 1846. 2 M 



