SILVER. 



According to the analyfis of Prouft, a variety of this ore 

 contained pearly .75 parts of metallic filver, and .25 ef 

 metallic arfenic. Red filver-ore occurs in veins, but is 

 always intermixed with other minerals, particularly with 

 compaft galena, cobalt, fulphuret of arfenic, native arfenic, 

 grey copper-ore, and fparry iron-ore ; and has a matrix 

 of calcareous fpar, fulphate of barytes, fluor fpar, or quartz. 

 It is a common ore in filver-mines, both in Europe and 

 America : the dark-red ore is confiderably more productive 

 than the light-red. 



S'thei- amalgam confilts of pure filver combined with mer- 

 cury. It has been found in the filver-mine of Salberg, in 

 the province of Dalecarlia, in Sweden, in the mines of 

 Deux-Ponts, in the Palatinate, and in fome other places, 

 either in thin plates or grains, or cryftalhzed into oftohe- 

 drons and dodecahedrons. It is fometimes femi-fluid. Its 

 colour is filvery-white or grey, the frafture conchoidal, and 

 the luftre metallic. It is foft, breaks when cut, and whitens 

 the furfaco of gold or of copper ; when rubbed upon them 

 warm before the blowpipe the mercury evaporates, and 

 leaves the filver pure. The conftituent parts, given by 

 Klaproth, are 



Silver 36 



Mercury ... - 64 



White Jilvtr- ore has a near refemblance to compaft galena. 

 The colour is a light lead-grey, pafTmg to fteel-grey : it 

 occurs maifive and dilTeminated, and is generally intermixed 

 with cubic galena. The frafture is mod commonly even, 

 but fometimes fine-grained and uneven, and alfo fibrous ; 

 the internaj luftre is glillening and metallic; the llreak 

 (hining. It is foft and brittle. The fpecific gravity is 5.3. 

 Some mineralogifts think this ore fhould be clafl'ed with the 

 argentiferous ores of lead. According to Klaproth, dif- 

 ferent fpecimens from Hemmels Furft, near Freyberg, 

 contain, of the 



Dark-white filver-ore. Light-white fiiver-ore. 



Lead - 41 48 



Silver - 9.25 20.40 



Antimony - 21.50 7.88 



Iron - 1.75 2.25 



Sulphur - 22.0 12.25 



Alumine - i.o 7 



Silex - 0.75 0.25 



Carbonate of Silver. — This ore has hitherto been only dif- 

 covered in the filver-mine of Winceflaus, in Swabia : it 

 occurs fometimes in maffes, and fometimes difleminated 

 through other minerals. Its colour is a greyifh-black ; 

 its fraclure uneven, with a glillening metallic luftre % it 

 is brittle and heavy, and effervefces with acids ; it melts 

 eafily under the blowpipe. According to Mr. Selb, who 

 firft defcribed this mineral, it contains 



of bifmuthic filver. Its colour is a light lead-grey : it oc- 

 curs difieminated, but rarely ever in mafies ; the frafture is 

 fine-grained, uneven, with a gliitening metallic luftre ; it is 

 loft and rather brittle ; before the blowpipe metallic glo- 

 bules appear on the addition of borax, which unite ; the 

 button is brittle, and of a tin-white colour : the flux ac- 

 quires an amber colour. According to Klaproth this ore 

 contains 



Silver 



Carbonate of antimony 



Carbonic acid 



72-5 

 17-5 

 12 



It contains alfo a flight trace of copper. 



Befides the above ores of filver, there are ores of other 

 metals which contain a portion of filver, and have been 

 claffed by fome mineralogifts with filver-ores. An argenti- 

 ferous variety of grey copper-ore, of an iron-black or fteel- 

 grey colour, has received the name of black filver-ore. It 

 occurs maflive, difieminated and cryftalhzed in tetrahe- 

 drons ; the frafture is fmall conchoidal, with a fhining me- 

 tallic luftre ; it is feftile and brittle. An ore which is a com- 

 bination of lead, bifmuth, aad filver, has received the name 

 I 



Lead 



Bifmuth 



Silver 



Iron 



Sulphur 



Copper 



33 

 27 

 15 



4-3 

 16.3 



0.9 



Argentiferous lead-ores are common in Great Britain and 

 in various parts of Europe. Many of thefe ores are not 

 fufficiently rich to repay the expence of extracting the filver. 

 It is procured in confiderable quantities in North Wales, 

 the north-weft parts of Yorkftiire, and in the counties of 

 Durham and Northumberland. Indeed, many lead-ores in 

 thefe counties contain a much larger portion of filver than 

 the average proportion of that metal in the ores of Mexico 

 and Peru ; but mineralogifts do not clafs them with filver- 

 ores. 



Silver Mines in Great Britain. — Silver-ores, properly fi> 

 called, are of rare occurrence in our ifland. A few years fince, 

 a vein of filver was worked with great profit in the parifh of 

 Alva, in the county of Stirling, in Scotland. The ores were 

 native filver, and vitreous filver-ore. From forty to fifty thou- 

 fand pounds fterling value was extrafted before the ore was 

 exhaufted, after which the fearch to recover the vein proved 

 fruitlefs, and fince that time no filver-mines have been worked 

 in that country. The filver-ores at Alva were accompanied 

 with copper, lead, and cobalt-ores, with a matrix of calca- 

 reous fpar, and fulphate of barytes. It is fuppofed by Dr. 

 Millar that the veins traverfe rocks of argillaceous por- 

 phyry. 



Cornwall and DevonlTiire yield the richeft argentiferous 

 lead-ores of any part of Great Britain ; but the quantity 

 of thefe ores is fmall. In the former county a fmall quan- 

 tity of native filver, with other filver-ores, have been occa- 

 fionally found. We have been favoured with the following 

 account of the prefent ilate of the filver-mines in thcle 

 counties from Mr. Mawe, author of Travels in Brazil, who 

 vifited them in the fummer of 18 15. 



From the lead-mines of Ben-Alften, in Devonftiire, 3 

 large quantity of filver has been extrafted. The vein is 

 fituated in killas, (fee Slate,) and is filled chiefly with 

 fluor fpar and galena. It has been worked to the depth of 

 1 10 fathoms : the filver extracted from the north and fouth 

 vein averages about 70 ounces to the ton of lead. Another 

 vein, running in a more eafterly and wefterly diredtion, 

 fituated in the fame killas, produces 170 ounces of filver in 

 the ton of lead. The vein is worked under the river Tamar. 

 Thefe mines are of confiderable importance ; during the laft 

 fix weeks, the filver extrafted from the lead procured here ■ 

 exceeded fix thoiifand ounces. The works are extenfive, 

 and faid to be well conducted. 



About four miles to the fouth-eaft of Callington is a 

 filver-mine of another defcription : the vein is fituated in a 

 fimilar rock of killas or chlorite Hate. The vein was firft 

 worked for copper, but native filver and lead-ore were difco- 

 vered in it. The mine is called Huel Jewel : the thicknefs 

 of the vein rarely exceeds three or four inches. In many of 

 the cavities were found a confiderable quantity of capillary 

 native filver, with galena, red filver-ore, and fulphuret of 



filvsr. 



