MELANITB. 151 



This analysis nearly agrees, both in the nature of the com- Pyroxene from 

 ponent parts, and in their proportions, with that which Mr. ^^ y^'^^qJS^^^ 

 Vauquelin has given of the crystallized black angite of 

 Etna ; iu which he found 



Silex 52 



Lime 13-20 



Alumine • 3*33 



Magnesia 10 



Oxide of iron 14.66 



- manganese 2 



95-19 



Hence we may consider these two stones as one variety, 

 though the quantities of lime and alumine are less in that 

 of Etna, and those of the other component parts on the 

 contrary greater. 



Analysis of Melanite. 



Another stone is met with at Frascati, and at A ibano, Bj^ck garnet, 

 near Rome, which is found in single detached crystals, and 

 has been called black garnet. 



Its form is that of the emarginated garnet of Hauy. By Descnbed. 

 trituration it yields a brownish gray or blackii-h pov;der. 

 Its specific gravity is 3-7. When heated red hot in a cru- Action of heat 

 cible it undergoes no observable change ; but before the on it. 

 blowpipe it rounds gradually into a globule. 



It is unnecessary to give the analysis in detail, as it was ^^ ^.^^ 

 conducted like the preceding, except that the oxide of iron 

 was precipitated by succinate of ammonia, and the following 

 method was pursued for detecting a fixed alkali. 



Sixty grains were decomposed by muriatic acid ; but this £^j^^;^ajio„ 

 was not effected completely till after several repeated diges- tor alkali, 

 tions. After separating the silex, the solution was decom- 

 posed by carbonate of ammonia. The ammoniacal liquor 

 was evaporated to dryness, the residuum redissolved in water 

 mixed with carbonate of ammonia, filtered, and evaporated 

 again. The salt, volatilized in a platina crucible, did not 

 give the least trace of a fixed alkaline salt. 

 ^ The 



