MEMOIR ON EMERY. 31 



diaspore of Schemnitz. For analysis it was decomposed with 

 carbonate of soda. It afforded : 



Pholerite of Gangue of diaspore 

 Guillemin. of Schemnitz — Smith. 



Silica 44.41 42.93 42.45 



Alumina 41.20 42.07 42.81 



Lime 1.21 trace and mag. trace. 



Water 13.14 15.00 12.92 



This corresponds to the following formula, Si A-l 4- 2B/; but 

 it is a question whether or not we should consider the water as 

 existing in any definite proportion, and whether or not they 

 did not all contain more water when first taken from their 

 localities. These hydrated silicates of alumina are numerous, 

 and bear various names ; but it is doubtful if many of them are 

 entitled to much consideration as distinct species. 



EPHESITE (A NEW SPECIES). 



This silicate is found with the emery of Gumuch-dagh, and 

 occurs on specimens of magnetic oxide of iron. It is of a pearly- 

 white color, and lamellar in structure; cleavage difficult. It 

 scratches glass easily, and has a sp. grav. of from 3.15 to 3.20. 

 Heated before the blowpipe it becomes milk-white, but does 

 not fuse. At first sight it might be taken for white disthene. 

 It is decomposed with great difficulty by carbonate of soda, 

 even with the addition of a little caustic soda. I used also 

 very successfully in the analysis the bisulphate of soda, either 

 in attacking the mineral from the commencement or in oper- 

 ating first with carbonate of soda, and then acting on the part 

 not decomposed with bisulphate of soda. The alkalies were 

 separated by means of hydrofluoric acid. 



Silica 31.54 30.04 



Alumina 57.89 56.45 



Lime 1.89 2.11 



Protoxide of iron 1.34 1. 



Soda with a little potash 4. 



Water 3.12 3.06 



Ml, 



LOO [ 

 L41 J 



This corresponds very nearly to the formula R 2 Si-)-3tl 2 Si+4H. 



ATOMS. AT. WEl&tfT. PER CENT. OXYGEN ItATIO. 



Soda 2 781.6 7.08 1 



Silica 6 3400 2 30.77 9 



Alumina 10 6416.2 58.08 15 



Water 4 450.0 4.07 2 



