CLASSIFICATION OP THI: MIXHRAL COLLHCTIONS IN THE 

 U. S. NATIONAL MUSEUM. 



By Wirt Tassin, 

 Assinlant Curator, Divmon of Aliiuraloyy. 



PREFACE. 



This outliue is preliminary to au exhaustive descriptive catalogue, 

 aud is issued iu response to numerous requests for methods of classifi- 

 cation, arrangement, etc. 



The series is divided into two general classes — native elements and 

 compounds of the elements. The compounds of the elements are further 

 divided and grouped under certain heads according to, and which take 

 their names from, their more negative constituents as follows: Com- 

 pounds of the halogens, fluorides, chlorides, bromides, and iodides. 

 Compounds of sulphur, selenium, and tellurium; also arsenic and anti- 

 mony, including sulphides, selenides, and tellurides; arsenides, anti- 

 monides, sulpharsenides, and sulphantimonides; also sulphosalts. 

 Oxygen compounds, including oxides and the oxygen salts, borates, 

 aluminates, chromites, ferrites, manganites, plumbates, arsenites and 

 antimonites, selenites aud tellurites, carbonates, silicates, titanates, 

 columbates aud tantalates, nitrates, vanadates, phosphates, arsenates 

 and antimonates, sulphates, selenates and tellurates, chromates, molyb- 

 dates and tungstates, iodates, and uranates. Compounds of organic 

 origin, including salts of organic acids and carbon comjiounds. 



Each of these classes is further separated into groups, the minerals 

 included in any one group being such as are related in the details of 

 chemical composition. Each of these groups is preceded by a general 

 group label giving the class to which it belongs, the group name, the 

 minerals composing that group, together with their chemical composi- 

 tion, system of crystallization, and a short description of the occurrence, 

 association, and characteristic form of each member of the group. The 

 following label will serve to give a clearer idea of this arrangement : 



Tungstates. 



Wolframite Group. 



Wolfraiiiite. (Fc,Mn)W04 Monocliiiic. 



Hiibuerite. MuWOj Monoclinic. 



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