ON THE INIEIONITE. ] ()C) 



II. Me ion it e. 



Mr. Mobs has attempted to raise clouljts respecting the MeVonite. 

 primitive form of the meionite, which he is desirous of as- 

 similating with that of the feldspar: but recent observations 

 made on specimens latel}' brought from Vesvivius, very well 

 marked and of a good size, have confirmed the angles, 

 both of the primitive and secondary forms, to be the same 

 as given by Mr. Haiiy in his Treatise on Mineralogj'. This 

 gentleman, having broken crystals of this substance, has 

 perceived joints parallel to tJie base, the position of which 

 was at first merely conjectured. These joints, it is true, 

 are not so clear as the lateral joints ; but this is agreeable 

 to the theory, which, giving a more extensive surface to 

 the bases than to the sides, explains why the sections paral- 

 lel to the bases are less easy to' hit upon than those of the 

 sides, where the points of contact are fewer. 



I have yet compared the meionite with the feldspar only Other charac- 



in respect to form; but there are other characters, such as ters beside form 



, . . .' employed uy 



specific gravity, hardness, lustre, fusibility, &c. The me- Haiiy. 



thod of Mr. Haiiy, which is not purely orictometrical, far 

 from excluding these, calls them in to the assistance of the 

 geometrical characters in determining the species. Now 

 Mr. Mohs says *, if the crystalline forms appear to militate 

 against the union of the meionite with the feldspar, the 

 other characters taken together will not allow us to part 

 them : otherwise the method ceases to be natural, since it 

 separates what nature has united. 



I shall not stop here to discuss the greater or less resem- The resem- 

 blance ascribed to the physical or chemical characters of j^^j ^q gJ^^ gg 

 the meionite with those of feldspar; a resemblance, which asserted. 

 does not appear to me so great as is said; for on the one 

 hand the meionite is strongly scratched by many pieces of 

 feldspar, and on the other, the latter does not melt before 

 the blowpipe like the former with ebulUtion accompanied, 

 by a hissing noise, as has been observed by Mr. Lelievre, 

 member of the council of mines, who is known to be very 



* Page 16 of th« paper already quoted. 



expert 



