GEOLOGICAL SOCIETY. 



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H. from 2 to 5. The ductility can in some in- 

 stances be only observed by the impression 

 which the corner of the hammer makes on 

 striking^ as in native arsenic. 



G. 10 and more, also without ductility, as mer- 

 cury. We have further examples in octa- 

 hedral bismuth, antimonial silver, hexahedral 

 silver, octahedral iron, &c. 



FOURTH ORDER — SULPHURETS. 



Metallic lustre : color gray or black. 

 H. from 1 to 5. 



G. from 4, 2 to 8, 5, as in gray antimony, Jam. ; 

 zinkenite, jamesonite, bournonite, prismatic cop- 

 per glance, Jam. ; polybasite, (H. Rose,) prisma- 

 tic melane glance, Jam. 



Streak, from brown to red, tesseral, without 

 distinct cleavage, and G. from 4, 2 to 5, 

 as in tetrahedral copper glance, Jam. 

 Ductile, very a dark gray to black, and G. 7 

 and more, as in prismatic tellurium glance, 

 and in hexahedral glance, Jam. We have 

 further examples in molibdan silver, tetra- 

 dymite, (Hdgr.,) hexahedral galena, peri- 

 tomous antimony glance, (Mohs,) Eucairite, 

 (Berzel.) and rhomboidal molibdena, Jam. 



