GALENA. 



little lustre. Colour lead-grey, wliicli in 

 some varieties inclines to blackish lead- 

 grey. On the surface sometimes shows an 

 iridescent tarnish. Lustre metallic. Opaque. 

 Structure lamellar. Cleavage parallel Avith 

 the planes of the cube, highly perfect and 

 easily obtained. Streak rather more shin- 

 ing than the surface of fracture. Sectile. 

 Easilv pulverised, and externally easily fran- 

 gible." H. 2-5 to 2-75. S.G. 7-25 to 77. 



Comp. Protosulphide of lead, or Pb S = 

 lead 86-6, sulphur 13-4=- 100. 



Silver and other metals are frequently 

 present, as Avill be perceived by the follow- 

 ing analysis of a specimen from Bottino, by 

 C.Bechi: 



Sulphur .... 12-840 



Lead 80700 



Antimony .... 3 •307 



Iron 1-377 



Copper .... 0-440 



Zinc 0024 



Silver 0-325 



99013 



BB decrepitates, then melts and emits a 

 sulphurous odour, and, when the sulphur 

 has been driven off, affords a globule of pure 

 lead, from which a grain of silver may fre- 

 quently be obtained b}'- cupellation. The 

 proportion of silver varies considerabi}', and 

 those varieties, the fractured surfaces of which 

 exhibit a granular structure, often contain 

 more silver than the more compact lamellar 

 varieties. Formerly it was not considered 

 profitable, in the north of England, to sepa- 

 rate the silver from the lead, unless the 

 former amounted to 6 ounces in the ton, and 

 in Wales unless it amounted to 12 ounces to 

 the ton. By the improved process, intro- 

 duced by Mr. Pattinson, it is now, however, 

 found profitable to extract the silver when 

 the lead does not contain more than 3 ounces 

 to the ton, at the same time that the cost of 

 refining is reduced from 60s. to 30s. per ton, 

 and the lead, after the separation of the 

 silver, is rendered much more valuable, 

 being less hard and brittle than before. 



Galena occurs in irregular deposits and 

 in veins in igneous and sedimentary rocks. 



Localities. — English. The largest crvstals 

 of Galena ever met with have been found at 

 the Laxey and Foxdale Mines in the Isle of 

 Man, some of which measure as much as 

 10 inches across. Fig. 202 represents the 

 prevailing form, but combinations of the 

 cube, octahedron, and dodecahedron also 

 occur. Octahedral crystals, of very large 

 dimensions, have also been found at Dufton 



GALEXA. 147 



and Alston, in Cumberland, and large cubic 

 crystals at Brownly Hill,in the same countv; 

 Cornwall and Devonshire, in veins travers- 

 ing clay-slate (Killas), Cumberland, Derby- 

 shire, Durham, Northumberland, Yorkshire 

 and Flintshire, in limestone. — Scotch Lead- 

 hills,inLanarkshire;Wanjock Head; in Dum- 

 friesshire ; and Monaltrie, in Aberdeenshire, 

 in granite ; Strontian, in Argyleshire, in 

 gneiss; Isla, in limestone; Coll, in gneiss. 

 — Foreign. Freyberg, in Saxony. Spain, 

 in the granite hills of Linares; also in 

 Catalonia, Grenada, and elsewhere. Ros- 

 mininhal, in Portuguese Estremadura. Sala, 

 in Sweden. Clausthal, Neudorf, and Pfaffen- 

 berg, in the Harz. Przibram, Miess and 

 Joachimsthal, in Bohemia. Schemnitz in 

 Hungary. Bleiberg, in Carinthia. The 

 Daouria mountains of Siberia. Algeria. 

 Cape of Good Hope. Australia. In the 

 United States extensive deposits of this ore 

 exist in Missouri, Illinois, Iowa, and Wiscon- 

 sin. The lead region of Wisconsin is stated 

 by D. D. Owen to extend 87 miles from east 

 to west, and 54 miles from north to south. 

 Within this area there is scarcely a square 

 mile in which traces of lead may not be 

 found. Although the diggings are seldom 

 more than 25 or 30 feet deep, as much as 

 1835 tons of ore have been raised from a 

 single spot not more than 5 yards square. 



Galena is the most abundant ore of 

 lead, and that from which the greatest 

 amount of the metal is obtained. In Hunt's 

 Mineral Statistics for 1859, a list of all the 

 lead mines in the United Kingdom will be 

 found, together with the quantities of ore 

 raised from each, and lead produced. The 

 total produce of the United Kingdom dur- 

 ing the year 1859 appears to be 91,735 tons 

 of ore, the value of which was £1,268,677. 



" Galena is distinguished from Plumbago 

 by its weight, and by its not affording dis- 

 tinct traces on paper; from Sulphuret of 

 Molybdena also by its structure, which is 

 never foliated ; and from the brilliant me- 

 tallic varieties of Blende, by the surfaces of 

 its crystals resuming their lustre instantly 

 when breathed upon, while those of Blende 

 remain dull for some time."— (Allan.) See 

 also Blue Lead and Speculak Galena. 



Name. From y»Xr'v^^ tranquillity, from its 

 supposed effects in mitigating the violence 

 of disease. 



Brit. Mus., Case 8. 



31. P. G. From the Grassington Mines, 

 in the Hall. Principal Floor, Case 15 (Isle 

 of Man and Ireland); Wall-cases 14, 25 

 L 2 



