1 78 Prof. Chapman on the Classification of Minerals. 



of its groups — that its leading divisions, indeed — are more or 

 less groups of convenience, cannot be denied; but with our 

 present restricted knowledge, there is no remedy for this. 



I propose to adopt four principal divisions or classes ; each 

 class including a certain number of families, and each family a 

 certain number of types or groups. The classes consist of — 

 (1), Metals and Thionoids; (2), Oxygen compounds; (3), Ha- 

 loids; and (4), Carbonoids. The term "thionoid" is used, as 

 a mineralogical term of general convenience, for sulphur and 

 sulphides, selenides, tellurides, antimonides, &c. 



In the present note, the first of these classes only will be con- 

 sidered. It comprises the ten following families : — I. Ferroids; 

 II. Pyrites; III. Blendes; IV. Glances; V. Argyroids; VI. Pla- 

 tinoids ; VII. Arsenoids ; VIII. Antimony Glances ; IX. Ruby 

 Blendes ; X. Sulphoids. A certain natural sequence has been 

 aimed at in the collocation of these families, and more especially 

 in that of their included types and species. The linear arrange- 

 ment necessarily presents an insurmountable obstacle to any great 

 success in this particular view ; but it is hoped that, with a few 

 manifest and unavoidable exceptions, each species will be found 

 more or less related to that which immediately precedes, and to 

 that which immediately follows it ; and this, independently of 

 the distribution of the species into types and families. Many 

 interesting relations, however, could only have been exhibited by 

 a parallel system of arrangement. 



I. Ferroids. 

 Native iron, native nickel, native copper. 



II. Pyrites. 



1. Chalkopyrite Type: — Dimetric. 

 Chalkopyrite Cu 2 S, Fe 2 S 3 ; cubanite (monometric?) Cu 2 S, 



Fe*S 3 + 2FeS. 



2. Phillipsine Type: — Monometric. 

 Phillipsine* (Buntkupfererz) 3Cu 2 S, Fe 2 S 3 . 



3. Stannine Type: — Monometric. 



Stannine 2Cu 2 S, SnS 2 + 2FeS, SnS 2 . Cubanite, phillipsine, 

 and stannine might perhaps be placed under one and the same 

 type. By simplifying the formulae, the first shows RS, the 

 second RS + 2R, the third RS. This latter is also the propor- 

 tional composition of chalkopyrite. 



4. Placodine Type: — Monoclinic. 

 Placodine Ni 4 As. 



* Phillipsite, Beudant, 1830. 



