4<44< Intelligence and Miscellaneous Articles. 



Silica 34-8 



Alumina 10"2 



Lime 8'4 



Magnesia I'S 



Protoxide of iron 18*0 



Deutoxide of manganese 5*0 



Water 14-4 98-9 



The formula for this mineral is, therefore, 

 (Ca O, Mg O, Fe 0)"+ (Si O^, Al^ O^, Mn,, O^)* + (H^ Oy, 

 supposing all the manganese to be in the state of deutoxide, and the 

 iron in that of protoxide. This formula is not simple, and probably 

 the composition may be really represented by the following some- 

 what different formida : — 



(Ca O, MgO, Fe 0)3+ (Si O', Al, O', Mn, 0)' + (Ho O)^ 

 This mineral differs essentially from the micas principally by the 

 large proportion of water which it contains. — Annates des Mines, 



torn. xvii. 



ON SODALITE AND CANCRINITE. 

 The sodalite of Ilmengebirge is distinguished from other known 

 varieties, especially by its generally very linej sapphire-blue colour, 

 varying in intensity in different specimens : it is not crystallized, 

 and is found only in small fragments. This mineral has the vitre- 

 ous lustre and is transparent ; it is not so hard as felspar ; its spe- 

 cific gravity is 2"288. It gelatinizes and dissolves in hydrochloric 

 acid. Before the blow-pipe it loses its colour, and fuses into a white 

 glass containing bubbles. 



According to Hoffmann's analyses performed in 1830, it is com- 

 posed of — Silica 38-40 



Soda 24-47 



Alumina 32-04 



Lime 0-32 95*23 



The loss of 4-77 consists of chlorine : from this analysis the follow- 

 ing formula is readily derived : — 



N3Si + 3AiSi+ NaCP, 

 a formula already given by M. Kobell, according to an analysis of 

 Arfwedson's, of the sodalite of Vesuvius, 



The cancrinite is very remarkable as a compound of a silicate and 

 a carbonate. Like the sodalite it is found only in small masses; it 

 cleaves readily in three directions, Avhich meet at angles of 120°, 

 parallel to the faces of a regular six-sided prism. 



This mineral is of a light red colour, transparent, of a vitreous 

 lustre on the cleavage faces, and of a greasy lustre in the other di- 

 rections ; its hardness is between that of apatite and felspar ; spe- 

 cific gravity 2-453. 



In hydrochloric acid, cancrinite dissolves with effervescence and 

 gelatinizes ; it becomes a white bubbly glass before the blow-pipe. 

 By calcination it lost 6-18 per cent. ; the residue effervesced but 

 slightly in hydrochloric acid, but still it gelatinized. It yielded by 

 analysis, — 



