24'i SILVER. 



ores of other metals, particularly with antimony, arsenic, bismuth, 

 and lead ; but occasionally the proportion of silver is insufficient 

 to repay the expence of extracting it. Silver ores occur princi- 

 pally in veins in primary and transition rocks, associated with 

 various earthy and metallic minerals. It has been remarked that 

 the warmer regions of the globe afford the greatest quantity of 

 gold, but the richest repositories of silver are situated either in the 

 higher latitudes, or in elevated regions. The most celebrated silver 

 mines of Europe are in Sweden and Norway, at no great distance 

 from the polar regions, and those which are in warmer latitudes are 

 almost all situated near the summits of alpine mountains, as at 

 Alternant, in France, and the mines of Mexico and Peru. Before 

 the blow-pipe, nearly all the ores of silver yield a globule of 

 metallic silver. "They dissolve in nitric acid, and the silver is 

 precipitated by the muriatic acid, forming a white insoluble matter, 

 that is reducible to a globule of metallic silver, which is not altered 

 by a continuance of the heat. The solution of silver in nitric 

 acid, tinges animal substances black, and deposits a coat of silver or 

 copper when immersed in it. These properties characterise the 

 ores of silver when they contain any notable portion of that metal." 

 Sp. 1. Native Silver. Pl. XXXII. fig. 1,2,3.— GediegenSilber, 

 Werner • Hexaedrisches Silber, Mohs. ; Argent natif, Hauy, iii. p. 

 384 ; Brong. ii. p. 248 ; Native Silver, Jameson, Syst. p. 42 ; Sow 

 erhjBrlt. Min. iv. p. 327. — Its colour is silver- white ; by exposure to 

 the air it becomes yellowish, or greyish black. It occurs massive and 

 crystalized in cubes, octahedrons, either regular or truncated on 

 the angles (Pl. 32, figs, h and a), four or six-sided prisms ; also in 

 tables and six-sided pyramids. It is frequently found in thin 

 membranes, capillary or reticulated, also dendritical and in leaves. 

 Native silver is softer than iron or copper, flexible, and malleable. 

 Its specific gravity is about 10. It is generally alloyed with a 

 small portion of antimony, gold, copper, or arsenic. It occurs 

 sparingly in veins, traversing clay-slate in several of the mines in 

 Devonshire and Cornwall ; in lime-stone, sand-stone, and 

 clay porphyry, in Stirlingshire, and other districts in Scot- 

 land ; in granite, in the Saxon Erzgebirge ; in gneiss and 

 mica slate at Konigsberg, in Norway, Saxony, and Bohemia. It is 



