388 Scientific Notices— Mineralogy. [Nov. 



Mineralogy. 

 7. Garnet. 

 To the numerous analyses which have already been published 

 of the individuals belonging to this important class of minerals, 

 we have to add the following : — 



1. Green trapezoidal garnet from the mine Gamla, in Sala. 

 Sp. gr. 3-746. 



Silica 36-62 18-42 oxygen 



Alumina 7*53 "> -, n .qi 



Oxide ofiron 22-18 J 1 "* 51 



Lime 31*80 \ g.gg 



Magnesia 1'95 J 



100-08 



2. The same, from the same locality, but obtained at a differ- 

 ent period. 



Silica 36-73 18-47 oxygen 



Alumina 2-78 \ q, 09 



Oxide of iron 25-83 J 



Lime 21-79 1 q.qo 



Magnesia 12-44 / J y ° 



99-57 

 (Bredberg, Kongl. Vet. Acad. Handl. 1822, p. 83.) 



3. Calcareous garnet, from Lindbo, in Westmannland. 

 Colour, black and blackish brown. Crystal, the primitive rhom- 

 boid, sometimes with truncated lateral edges. 



Silica 37-55 18-78 oxygen 



Oxide of iron 31-35 9-61 



Lime 26-74 . . . 



Oxidule of manganese. 4-78 ... 



100-42 



(Hisinger, ibid. 1821.) 



These three analyses accord sufficiently with the formula 

 which has been deduced as representative of the constitution of 

 garnet ; namely, an atom of a silicate of a base containing two 

 atoms of oxygen + an atom of a silicate of a base containing 

 three atoms of oxygen. 



The mineralogical formula for the Sala garnet is 



m} s+ f} s 



and for the Lindbo garnet, 



C U+FS 

 mgj 



} 



8-65 



