Natural System in Mineralogy. 117 



metallic lustre, is divided into six tribes, which are : 1. 

 Metalloids, — native metals and metal-like elements ; 2. Ga- 

 lenoids, — argentite, galenite, stannite, chalcopyrite, pyr- 

 rhotite, alabandite, etc. ; 4. Smaltoids, — smaltite, niccolite, 

 breithauptite, with other arsenids, antimonids, etc. ; 5. Ar- 

 senopyritoids, — including arsenopyrite, cobaltite, etc. ; 6. 

 Bournonoids, — enargite, bourn onite, zinkenite, etc. The 

 various selenids and tellurids form subtribes distinct from 

 the sulphurous or Thiogalenoids. In the second suborder 

 are included those species more or less resinous or adaman- 

 tine in lustre, generally red in color or in streak, and often 

 transparent or translucent, whence the distinctive name of 

 Spathometallates. In this suborder we distinguish at least 

 two tribes : 1. Sphaleroids, corresponding to galenoids, and 

 including cinnabar, realgar, christophite, marmatite, spha- 

 lerite, greenockite and hauerite,; 2. Proustoids, correspond- 

 ing to bournonoids, and embracing proustite and other red 

 silver ores, tetrahedrite, livingstonite, dufrenoysite, binnite, 

 etc. It is worthy of notice that while sulphid of mercury, 

 in the forms of metacinnabar and cinnabar, appears in both 

 suborders of the Metallates, the sulphid of antimony is also 

 represented among the Spathometallates by the red and 

 generally uncrystalline kermes. The various forms of sul- 

 phur and of phosphorus, together with vitreous selenium, 

 will constitute a third tribe of the second suborder of Metal- 

 lates. The Spathometallates, as seen in their typical forms, 

 sphalerite, wurtzite, greenockite, cinnabar, proustite, etc., 

 serve, through the sulphoxydates, kermesite and voltzite, 

 and through sulphosilicates like helvite anddanalite, to con- 

 nect the order of Metallates with spathoid Oxydates and 

 Silicates. 



In these various tribes the relations of hardness to con- 

 densation are not less apparent than in Silicates and Oxy- 

 dates. Dividing the simplest atomic formula of the complex 

 Metallates by the number of atoms, we get, as the most con- 

 venient term for comparison, the mean weight of the ele- 

 mental unit from which to deduce the volume V. We thus 

 find for the pyritoids, pyrite and marcasite, values for V 

 of 4-0 and 4"2; for linnseite, 44; for pyrrhotite and chal- 



