332 Letter from Mr. Breithmipt to Prof. Gilbert. [May, 



fying mineral bodies according to their characters. It is true 

 that boracite has been arranged among the salts, like a fish with 

 stag's horns. Although its quavtzy hardness, long ago well 

 known to Ilsemaim, showed clearly that it belonged to the 

 precious stones. 



I presume likewise that boron exists in helvine, dioptase, 

 sphene, cyanite, tetrahedral fahlore, and oven in Rothgilti- 

 gerze. I am almost certain that boron is a constituent of 

 wolfram. 



All this is nothing to the number (above 40 species, according 

 to Wemer's system) of minerals in which theory has pointed out 

 to me the existence of chlorine as an essential constituent some- 

 times generically, sometimes specifically, though analytical 

 chemistry has not been able hitherto to verify these theoretical 

 conclusions. Thus it exists in schaumkalk, talc, mica, schiller- 

 stone, felspar, cyanate, &.c. and in many imcrystallized minerals, 

 as steatite, serpentine, nephrite, chalk, mountain soap, fuller's 

 earth, &,c. One will not easily miss chlorine in a fatty, soft 

 mineral, and the talky properties are produced not less by it than 

 by magnesia. 



As chlorine and iodine resemble each other very closely, but 

 the latter has more of the metallic properties, I presume that 

 both, but more probably the latter, exists in graphite, molybdena, 

 blcittererz, black earthy cobalt, manganschaum, 8cc. A person 

 may easily satisfy himself that the essential constituent of 

 graphite is not yet known, and that a substance exists in it 

 which has not yet been shown experimentally to constitute a part 

 of the mineral kingdom. 



But I must be shorter than I have been. I write at present 

 on purpose to obtain the assistance of chemists. Already has 

 chemistry been of the greatest service to mineralogy ; and it is 

 now time that this last science should atone for her faiUts 

 towards her benefactor. 1 hope within a year to publish a 

 System of Mineralogy which will not merely consider crystals 

 and crystallized species as belonging to pure natural history, but 

 with respect to which chemists will have no reason to complain 

 of intolerance. August Breithaupt, 



Freiberg, Aug. 6, 1818. 



