126 ECONOMIC GEOLOGY 



sumed at home. Some lead is brought in duty free. This has 

 considerable influence upon the annual statistics of the metal. 

 The total valuation of metallic lead and all the pigments derived 

 therefrom has in some years exceeded $60,000,000. 



Mercury : Its Properties, Occurrence and Uses. 



Properties. Mercury, symbol Hg, is a bright, silver white, 

 metal, liquid at ordinary temperatures. It was this physical 

 property that gave the metal the old name of quicksilver. It 

 is the only metal liquid at ordinary temperature. Bromine is 

 the only other element liquid at normal temperature. At 38.8 

 below zero mercury crystallizes in the isometric system. The 

 malleable and ductile cubes are of higher specific gravity than 

 the liquid metal. The liquid metal emits vapor at ordinary 

 temperatures. It does not tarnish upon exposure. It is not 

 attacked by HC1, nor by concentrated H 2 S0 4 without heat. 

 It is readily soluble in HNOa. Its specific gravity as a liquid 

 is 13.59, as a solid it is 14.19. Its boiling point is 357. Its 

 atomic weight is 200. 



Ores of Mercury. Native mercury, Hg, is rare but sometimes 

 reported in considerable quantity. 



Cinnabar, HgS, 86.2, per cent, of mercury. The only cochineal 

 red mineral entirely volatile before the blowpipe. 



Metadnnabarite, 86.2 per cent, of mercury. The black sul- 

 phide of mercury. 



Calomel, HgCl, 84.9 per cent, of mercury. Most abundant 

 in Carniola and Spain. 



Tiemannite, HgSe, 71.7 per cent, of mercury. The selenide 

 of mercury which was once worked in the Lucky Boy claim in 

 Utah. 



Living stonite, HgS,2Sb 2 S3, 24.8 per cent, of mercury. A 

 double sulphide of mercury and antimony that has furnished a 

 small amount of the metal in Mexico. 



Amalgam, HgAg, is an alloy of silver and mercury in varying 

 proportions. The mercury may be as low as 5 per cent, or as 

 high as 73.6 per cent. 



Origin of the Ores. Mercury, unlike the precious and most 

 of the useful metals is not very abundant nor widely diffused 

 in nature. It must, however, be remembered that owing to its 

 volatility minute traces of the metal may be easily overlooked. 



