144 Washington — Suggestion for Mineral Nomenclature. 



for euphony or to avoid confusion with ordinary chemical 

 salts), will be affixed the termination used in inorganic chem- 

 istry for the type of compound represented. For the mineral 

 acid itself this termination would then be -ic, for a binary com- 

 pound (oxide, sulphide, etc.) it will be -ide, for the sulpho-acid 

 and analogous salts,*, and for the oxy-acid salts, it will be -ate. 

 As noted above, it will not be necessary to know the constitu- 

 tional formula of the acid or mineral group to name it, as it 

 may be defined by its empirical formula and crystal form. 



The water of crystallization of hydrated mineral salts may 

 in general be considered for the purposes of nomenclature as 

 part of the negative portion of the molecule, since not only do 

 nearly all hydrates differ crystallographically from the anhy- 

 drous salts, but the crystal form varies with the number of mole- 

 cules of water present when several hydrates exist. 



Such simple designations, implying always the crystal system 

 characteristic of the salts of the mineral acid, will suffice for 

 the negative (acidic) portion of isomorphous mineral groups in 

 which the acid radical is identical in all (the base alone varying 

 through isomorphous replacement), or for monotypic mineral 

 groups. Thus, the members of the calcite, aragonite, and 

 olivine groups are respectively salts of calcitic, aragonic, and 

 olivinic acids, or calcitates, aragonates, and olivinates ; while 

 cyanite and calamine are the only known disthenate and cala- 

 mate respectively. 



When, however, in a group the chief element in the acidic 

 portion is replaceable isomorphonsly, by different elements, as 

 with the pyrite and apatite groups or, as in the pyroxenes and 

 feldspars, there are marked differences in the crystal symmetry, 

 the acidic portion remaining chemically the same, it becomes 

 necessary to indicate these differences in the nomenclature. 

 This may best be done in two ways, according to which of the 

 cases is involved. 



In the case of isomorphous replacement in the acidic portion 

 the different compositions may be expressed by the use of 

 appropriate prefixes to the acidic term used without a hyphen. 

 Thus all members of the pyritohedrally isometric pyrite 

 group would be pyrides, but pyrite and hauerite would be 

 sulpyrides, and smaltite and chloanthite arsenpyrides. Among 

 the silicates the presence of unusual or non-typical elements 

 partially replacing silica may be expressed by similar syllables 

 prefixed to the acidic name with a hyphen. Thus rosen- 

 buschite and lavenite would be zirco-diopsidates. In some cases, 

 when the isomorphous replacement in the acidic portion is 

 complex, it may be advisable to use very much shortened syl- 



* The regular termination -ite would be inadvisable for these, as liable to 

 confusion with present names. 



