SILVER ORES. 75 



SILVER. 



Silver ores are easily fused before the blowpipe flame, 

 either with or without carbonate of soda. The resulting 

 globule of metal, of its characteristic white colour, can bo 

 readily hammered out or cut by a knife. 



If the powdered mineral, supposed to contain silver, be 

 dissolved in nitric acid and the solution be filtered or de- 

 canted, the presence of silver may be known by adding a 

 solution of common table salt or of hydrochloric acid to 

 the original solution. If silver be present, a white precipi- 

 tate is thrown down. As chloride of lead or mercury might 

 also be precipitated, let it be remembered that chloride of 

 silver is soluble in ammonia, whereas chloride of lead is un- 

 changed, and mercurous chloride blackened by it. 



A very bright piece of copper, placed in the original solu- 

 tion, would be coated with metallic silver, if any existed. 

 To test for copper, a bright knife-blade dipped into the solu- 

 tion would be coated with a copper film. 



Sometimes, if a lump of silver-bearing ore be placed in a 

 very hot fire, it will show white particles of the metal on 

 the outside. 



The silver metal soon tarnishes, when exposed to the 

 action of sulphur ; thus, if boiled along with the yolk of an 

 egg, it will blacken 



Native Silver. 



Found as wire silver, in thin sheets, in tree-like shapes, 

 &c., and as octahedral crystals. 



Colour and Streak silver white. When found in veins 



is usually tarnished on the surface. 

 Structure easily cut and hammered out. 

 H. 2-5 to 3; S.G. 10-1 to 11-1. 



The silver usually contains gold and copper. Is recog- 

 nised by the blowpipe and acids, as above mentioned. 

 Native silver is often associated with iron rocks, native 

 copper, &c. 



Brittle Silver Ore (sulphide of silver and antimony). 

 Found massive, compact, in rhombic prism crystals, &c. 



