46 Sketch of the latest Improvements [Jan. 



from Iceland, and by different other mineralogists, seems to me to 

 be very nearly connected, if not quite the same, with wliat I have 

 called native carbonate of magnesia from India ; though its external 

 characters, according to the following description, are not quite the 

 same. This difference I ascribe to the abseace of carbonate of iron 

 in the Indian mineral. 



Conite has a light flesh-red colour. It is amorphous, and exter- 

 nally covered with a coating of iron ochre. Fracture sometimes 

 fine-grained, uneven ; sometimes imperfectly conchoidal. No 

 lustre; scratches glass ; opake ; brittle; sp- gr. 3-000. 



Its constituents, according to the analysis of Dr. John, are as 

 follows : — » 



Carbonate of magnesia 67'5 



lime 28-0 



iron 3-5 



Water 1 



Sulphate of lime ? a trace. 



lOO'O 



9. Zeolite. — Haliy's division of the zeolite into stilbite and meso- 

 type is well known ; and likewise his union of the natrolite with 

 the mesotype. Gelilen analysed two specimens of each of these 

 genera. The following was the result : — 



Gelilen has rendered it probable that the mineral analysed by 

 Vauquelin under the name of mesotype pyramidee, and even the 

 minerals tried by Haiiy before the blow-pipe, were not mesotypes, 

 l)ut stilbites. We see from the preceding analysis that the two 

 minerals constitute two distinct species, well marked by the propor- 

 tion of their constituents. Stilbite contains twice the water in 

 mesotype. Mesotype contains much less lime, but much more 

 alkali. 



10. Boracite. — About five years ago boracitc was found in abun- 

 dance by Professor Steffens, in a gypsum mountain near Segeberg, 

 in Holstein. The crystals are very small, and consist either of 

 perfect cubes, or of cubes with their angles truncated. Aceording^ 

 10 the analysis of Professor Pfaff!. this boracite is composed of 



