598 MANUAL OF NATUEAL HISTORY. 



4. Family. — Rhodiides. Minerals containing Rho- 



dium. Occurs in platinum-ore ; extremely 

 insoluble, brittle ; sp. gr. 11. Symb. R. 



5. Family. — Rutheniides. Minerals containing 



Ruthenium. Occasionally present in pla- 

 tinum-ore, also in " Iridosmine f when pure, 

 brittle ; sp. gr. 8*6. Symb. Ru. 



IIT. ORDER — Akgyrexides. 



Metals of the silver series, either native, alloyed, 

 or in combination with other substances ; solid or 

 liquid. 



1. Family. — Argyrides. Minerals consisting of, 



or containing chiefly, silver. Occurs 1, native, 

 either massive, or in cubical or octohedral 

 crystals, H. 2*5-3, sp. gr. when pure, 10*51 ; 

 2, in combination with sulphur, as " Silver 

 Glance/' H. 2-2*5, with antimony as " Anti- 

 monial -Silver/' H. 3*5-4, or with both as 

 " Miargyrite " and " Pyrargyrite," H. 2-2*5, 

 with bismuth as " Bismuth-Silver/' and in 

 various other states. Found mostly in cal- 

 careous-spar or quartz veins, in gneiss and 

 early slate rocks. Silver is soluble in nitric 

 acid, from which hydrochloric acid, or a so- 

 luble chloride, as common salt, throws down 

 a white insoluble chloride of silver. Symb. 

 Ag. 



2. Family. — Hydrargyrides. Minerals consisting 



of, or containing chiefly, mercury. Occurs 1 , 

 native, liquid, sp. gr. 13*545, in Carniola and 



