as a Branch of Natural History^ ^c. 249 



part of the tube. Many give out a sulphurous smell by mere friction. Lustre 

 generally strong and specular, either externally or internally. 



Family I. — Pyrites. 

 Fracture seldom lamellar, generally uneven, granular, or small conchoidaL 

 For the most part hard, scratching felspar, or at least calcareous spar. Spe- 

 cific gravity from 6.5 to 4.1. External lustre generally more splendent than 

 the intemaL 



f Hard (not scratched by steel) and compact. 



Gen.— Iron pyrites ; white iron pyrites ; arsenical pyrites (with Weissenerz, 

 W., or argentiferous arsenical iron). 



•j- f Hard, with foliated structure. 

 Getu — Cobalt glance (with sulphuret of cobalt ( Wernekink\ and bright or 

 silvery white cobalt) ; magnetic iron pyrites ; tin pyrites. 



•)• -f -j- Soft (scratched by steel) and compact. 

 Gcw.— Copper pyrites ; grey copper ore (with arseniferous grey copper, an- 

 timoniferous grey copper, and arseniferous and antimoniferous grey copper). 



Family 2. — Galenas or Glances. 



Structure more or less foliated ; fracture even, or large and flat conchoidal ; 

 generally soft, scratching at most calcareous spar or talc. Specific gravity 

 7.5 to 4.5. Internal lustre very strong ; external generally weak. 



•f- Malleable. 



Gen — Silver glance. 



ft Brittle. 



Gen. — Brittle silver glance ; lead glance (with argentiferous, seleniferous, 

 bismuthiferous lead glance, and WeissguUigerz or white silver) ; Boumonite ; 

 black tellurium ore {Nagyager-erz, W., or Bl'dttertellur, Leonhard) ; copper 

 glance, or vitreous copper ore ; Tennantit ; bismuth glance (with bismuthife- 

 rous bismuth glance, or Bismuth sulfureux, Haiiy ; cupriferous bismuth glance, 

 and Nadelerz) ; sulphuret of nickel, or capillary pyrites ; grey antimony ; sul- 

 phuret of molybdena. 



Appendix to the Family G/ances— Cupriferous grey antimony, with endel- 

 lione or Boumonite of St Harey ; nickeliferous grey antimony ; Jamesonite ; 

 Zinkenite ; Haidingerite (Berthier) ; Polybasite ; flexible sulphuret of silver 

 (Bournon) ; prismatoid copper glance (Mohs) ; Stembergite. 



Appendix to the Order Pyrites. 

 Nickel glanz (Berzelius) ; arsenic glanz (Breithaupt) ; alloy of nickel and 

 antimony (Brard), or sulpho-antimoniuret of nickel (Beudant) ; Ajcotomer arse- 

 nic kies, or axifrangible arsenical pyrites (Mohs) ? 



Order IV.— GRAPHITES. 



Chem. iVo^— Carburets or carbon mixed with iron or earthy substances. 

 Detonating with saltpetre ; burning without flame or smoke. Specific gra- 

 vity not exceeding 2.2. Very sofl, scratching only talc, or at most gypsum. 

 Gen.— Graphite ; glance coal (anthracite). 



