SILVER. 149 



light-red silver ore, and is characterized by the red colour which 

 all the varieties yield when powdered. The prevailing colour is 

 cochineal red, passing into lead -grey and iron-black. It occurs 

 crystalized in a great variety of forms, also disseminated, amor- 

 phous, in grains, or botryoidal, dendritical, reniform, cellular, and 

 in leaves. According to Hauy, the primitive form is an obtuse 

 rhomboid (fig. b.) The number of secondary forms known to 

 mineralogists are 14. The most common are an equiangular, 

 six-sided prism, or a six-sided prism terminated by three rhorn- 

 boidal faces, (fig. c.) In dark red silver ore the streak is cochineal 

 red ; in the light red variety the streak is aurora red. The struc- 

 ture is laminar. The fracture is uneven or imperfectly conchoidal 

 with a shining lustre. It yields easily to the knife, and is very 

 brittle. The specific gravity is about 5 '6. It decrepitates before 

 the blow-pipe, and melts with a slight effervescence, emitting a 

 white vapour, and leaving behind a globule of metallic silver. It 

 consists according to Thenard, of 58-4 oxide of silver, 23*5 oxide 

 of antimony, 16 of sulphur. With respect to its distinctive charac- 

 ters, Mr. Bakewell observes, " Cinnabar .realgar, red antimony, red 

 copper ore, black sulphuret of copper, and sulphuret of silver, have 

 some resemblance to red silver, but may be distinguished by the 

 following characters : — Cinnabar, realgar, and red antimony, are 

 entirely volatalized by the blow-pipe if pure ; their specific gravity 

 varies considerably from that of red silver ; red or ruby copper 

 effervesces in nitric acid, and the solution communicates a blue 

 colour to ammonia ; black sulphuret of copper or vitreous copper 

 yields a blackish streak. Sulphuret of silver has a greater specific 

 gravity, and does not yield a red streak. Red silver ore accompa- 

 nies other ores of silver in veins traversing gneiss, mica slate, 

 porphyry, and greywacke, in many of the mining districts, as Corn- 

 wall, Hartz, Saxony, Hungary, Mexico, and Peru. 



Sp. 7. White Silver Ore. — Weissgultigerz, Werner ; Plomb 

 sulfure antimonifere et argentifere. Hauy ; Argent blanc, Bro7ig. 

 — The prevailing colour is pale lead-grey. It occurs massive and 

 disseminated, and always associated with lead glance. The fracture 

 is even and fine grained, sometimes fibrous. It is soft and 

 somewhat brittle. The specific gravity is 5*3. An analysis of 



Y 



