30 



MEMOIR ON EMERY. 



not astonishing to see this connection of alumina more or less 

 hydrated with a hydrate of alumina of definite composition. 



After a knowledge of this fact one might seek to explain 

 the existence of water in corundum by the intimate mixture 

 of diaspore with this mineral. If this be the case, the crystal 

 of corundum from the Carnatic, which gave me three per cent. 

 of water, must contain twenty-three per cent, of diaspore, al- 

 though neither the eye nor the microscope could detect its 

 presence. 



As to the properties of diaspore, I have nothing to add to 

 what has already been published on the subject, except that 

 the specimens I examined do not decrepitate to the same extent 

 as that of Siberia. Its specific gravity is 3.45, and hardness 

 above 7. The following analyses were made, the mineral 

 being attacked with the bisulphate of soda. They afford the 

 formula XI H. 



Localities. 



Gumuch-da^h 0.67J 82.20 



Gumuch-dagh 0.82' 83.12 



^axos 0.26 82.94 



0.41 



trace. 

 0.35 



1.20 

 0.6G 

 1.06 



trace, 

 trace. 



14.52 

 14.28 

 14.81 



ZINC SPINEL. 



I possess a single specimen of this spinel in chloritoid on a 

 piece of emery from Gumuch-dagh. It is in octahedral crystals 

 agglomerated, of a dark emerald-green color. The quantity 

 being small, I have been prevented from making an exact 

 analysis. The quantity of oxide of zinc appears to be from 

 thirty to forty per cent. 



PHOLERITE. 



A mineral resembling pholerite in composition has been 

 found with the emery of ]^axos associated with emerylite. It 

 is white, lamellar, and somewhat crystalline, sometimes gray. 

 It is soft to the touch like steatite, infusible before the blow- 

 pipe, and when heated with nitrate of cobalt becomes strongly 

 colored blue. It is scratched with the nail, and has a specific 

 gravity of 2.564. Its composition is identical with the pholerite 

 of Guillemin, also with the mineral forming the gangue of the 



