MULL. MINERALS. 579 



mineralogists, and the description, however imperfect, 

 will therefore be of use, by directing their attention 

 towards it, and thus, possibly, ascertaining its existence 

 in other places. 



Its external characters are very limited, since it con- 

 sists of a loose white powder, somewhat coarser than 

 silica as it is obtained from the silicated alkalies, gritty 

 between the teeth, but not so hard as to scratch 

 glass. 



It does not effervesce with acids, and before the blow- 

 pipe it melts immediately into a transparent colourless 

 bead with apparently the same facility as glass. It is 

 certainly at least more fusible than datholite. I have 

 not been able, from its condition, to determine its spe- 

 cific gravity. On attempting to analyze the very minute 

 quantity that could be spared for that purpose, it was 

 found to consist principally of silica. A small quantity 

 of lime was taken up by muriatic acid, but its fusibility 

 was not destroyed by that treatment. When treated 

 however in a similar manner with sulphuric acid, the 

 fusibility was destroyed. No alkali was found in it, nor 

 any boracic acid, nor any traces of metallic matter. It 

 is not easy therefore to account for its great fusibility 

 unless it should contain the new alkali. In this uncertain 

 state must its chemical composition remain, until other 

 specimens are procured to admit of a repetition of these 

 experiments on a more extensive scale. 



It is found filling irregular cavities in the amygdaloid 

 of the valley above mentioned, so well known to mine- 

 ralogists ; where it is accompanied by analcime, mesotype, 

 prehnite, and calcareous spar. There is no appearance 

 of decomposition in the accompanying minerals, and I 

 may add that the specimens in question were broken 

 from a fresh rock in which they were deeply imbedded. 



The preceding characters seem sufficient to distin- 

 guish it for the present from all the mineral substances 

 hitherto described ; and the term conite appears well 



