602 MANUAL OF NATURAL HISTORY. 



1. FAMILY. Molibdides. Minerals containing lead, 

 either native or in combination. Occurs 1, 

 native, monometric, H. 1-5, sp. gr. 11 -381 ; 

 very rarely ; 2, as Sulphuret or " Galena," 

 monometric, H. 2 '5, sp. gr. 7'5, colour and 

 streak lead-gray, easily fused, frangible, in 

 beds and veins in crystalline and uncrystalline 

 rocks ; 3, as Oxide or " Minium/' pulverulent, 

 in minute rhombic prisms ; sp. gr. 4 '6, in 

 veins of galena and calamine ; 4, as Car- 

 bonate or "Cerusite," in right rhombic 

 prisms, H. 3-3 '5, sp. gr. 6 '4, lustre adaman- 

 tine, colour white or gray, very brittle, in 

 many lead mines ; 5, as Phosphate or "Pyro- 

 morphite," in hexagonal prisms, H. 3-5-4, 

 sp. gr. 7 ; colour green, yellow, or brown ; 

 lustre resinous, brittle, in veins with other lead 

 ores ; 6, also less frequently combined with 

 selenium, tellurium, antimony, arsenic, va- 

 nadic, chromic, molybdic, and tungstic acids. 

 Metallic lead fuses at 612F., its soluble salts 

 give a black precipitate with hydrosulphuric 

 acid. Symb. Pb. 



2. FAMILY. Baryides. Minerals containing com- 

 pounds of Barium. Occur 1, as Sulphate of 

 Baryta or "Heavy-spar," tabular, H. 2 -5-3 '5, 

 sp. gr. 4'7, white or grayish -blue, in metallic 

 beds, or in distinct veins in secondary limp.- 

 stone ; 2, as Carbonate or " Witherite," 

 trimetric, in large masses, H. 3'5, sp. gr. 4'30, 

 white, brittle, with lead ore, in coal formations. 



