SILVER ORES. 329 



particles of copper are removed, and f. surface of fine silver 

 is left. Silver is much less malleable than gold, and can- 

 not be beaten into unbroken leaves less than 100,000th 

 part of an inch thick. 



In expressing in the arts the purity of silver, if absolutely 

 pure, it is said to be silver of 12 pennyweights ; if it con 

 tain yiy of its weight of alloy it is called silver of 1 1 penny 

 weights ; if 2-12ths be alloy, it is called silver of 10 penny 

 Weights, and so on. 



silver glance. — Sulphuret of Silver. 



Monometric. In dodecahedrons <nore or less modified 

 Fig. 22a, page 30, and also other modifications. Cleavage 

 sometimes apparent parallel to the faces of 

 the dodecahedron. Also reticulated and mas- 

 sive. 



Luster metallic. Color and streak black- 

 ish lead-gray ; streak shining. Brittle. H = 

 2—2-5. Gr = 7*19— 7*4. 



Composition: when pure, silver 87*04, sulphur 12*96. 

 Before the blowpipe it intumesces, gives off an odor of sul- 

 phur, and finally affords a globule of silver. Soluble in di- 

 lute nitric acid. 



Dif. Resembles some ores of copper and lead, and other 

 ores of silver, but is distinguished as a sulphuret by giving 

 the odor of sulphur before the blowpipe, and as an ore of 

 silver by affording a globule of this metal, by heat alone. 

 Its specific gravity is much higher than any copper ores, and 

 it is sectile. 



Obs. This important ore of silver occurs in Europe, 

 principally at Annaberg, Joachimstahl, and other mines of 

 the Erzgebirge ; at Schemnitz, and Kremnitz, in Hungary, 

 and at Freiberg in Saxony. It is a common ore at the Mex 

 ican silver mines, and also in the mines of South America. 



A mass of sulphuret of silver, is stated by Troost, to have 

 Deen found in Sparta, Tennessee. It also occurs with na- 

 ive silver and copper in Northern Michigan. 



Uses. This is a common and highly valuable ore of sil 

 ver. 



Besides this sulphuret of silver there are two others, which contain 

 also sulphuret of iron or copper. 



What is the appearance of vitreous silver 1 What is its composition ? 

 What is its value ? How is it distinguished 1 



