174 



ZINC. 



An alloy of zinc and iron has been observed in a 

 zinc manufactory at Bristol. It lined the tube 

 leading from the retort. It was hard and brittle ; 

 the fracture showing the broad facets like zinc, but 

 of a duller gray colour, with surfaces more rough 

 and granular. Its specific gravity was 7' 17-. It 

 consisted of 92-6 zinc and 7*4 iron. 



The ores of sine are five in number; viz. blende, 

 red oxide of zinc, electric calamine, calamine, and 

 white vitriol. 



1. Blende occurs crystallized in rhombic dodeca- 

 hedrons, octahedrons, and in numerous intermediate 

 forms. It cleaves with facility parallel to the faces 

 of the rhombic dodecahedron, which is the primary 

 form of its crystals ; lustre adamantine ; colour red- 

 dish-brown, black, yellow and green ; streak white 

 to reddish-brown ; hardness equal to that of apatite ; 

 specific gravity 4*5 to 4*8. It occurs massive also, 

 as well as in crystals; structure curved, lamellar, 

 columnar, granular and impalpable. Composition, 

 according to the analysis of doctor Thomson : 



Zinc, 



Sulphur, 



Iron, 



23-16 

 808 



Blende occurs in primitive and secondary rooks, and 

 is found associated with galena and copper pyrites. 

 It abounds in England, Scotland, Saxony, Carin- 

 thia, and other European countries. It is the ore 

 which affords the zinc of commerce. Specimens 

 from some localities are phosphorescent, with a 

 yellow light simply on friction. This is the case 

 at Schlackenwald, Bohemia, in the Hartz, and in 

 Perthshire. The splendent fibrous variety from 

 Przibram contains a small proportion of the rare 

 metal cadmium. This metal has likewise been de- 

 tected in the radiated blende of Freyberg and Der- 

 byshire. 



2. Red oxide of zinc. This interesting ore pos- 

 sesses only a lamellar structure, never having been 

 met with in perfect crystals. It yields to cleavage, 

 parallel to all the faces of a regular six-sided prism. 

 Its colour is ruby or blood-red. It is translucent, 

 with a shining lustre. By long exposure to the 

 weather, it suffers decomposition at the surface. It 

 is easily scratched by the knife ; specific gravity 

 6-2. It consists of oxide of zinc 88 and red oxide 

 of manganese 12. It is infusible before the blow- 

 pipe, excepting when mixed with sub-carbonate of 

 soda, in which case, it melts into a transparent yel- 

 low bead. Its only localities are Franklin and 

 Stirling, New Jersey, where it occurs along with 

 ores of iron and manganese. 



3. Electric calamine. This ore occurs crystal- 

 lized, stalactitic, mamillary, and compact. The 

 crystalline forms are numerous ; the primary form 

 is that of a right rhombic prism of 102 30' arid 77 

 30'. The crystals are not often solitary, but most- 

 ly disposed in radiating groups. It varies from 

 transparent to translucent or opaque. Its hardness 

 is above that of apatite ; specific gravity 3-4. Its 

 colours are grayish, bluish and yellowish- white, or 

 possessed of some tinge of green ; and occasionally 

 it presents a brownish or blackish colour. It con- 

 sists of 



Oxidr- of zinc, 



SiU'x. 

 \V.,: r. 



68-3 

 25- 

 4'4 



When gently heated, it is strongly electric ; some 

 varieties become so by friction. Before the blow- 

 pipe, it is infusible, but loses twelve per cent, by 

 ignition. Its native localities are in primitive and 



secondary rocks. It is found at Retzbania in Hun- 

 gary, at Bleiberg in Carinthia, and at Freyberg in 

 the Brisgau. In Scotland, it is found in the It-ad 

 mines of Wantockhead. It also occurs in Wales 

 and England. 



4. Calamine. This valuable ore is found crystal, 

 lized, pseudimorphous and massive. The crystals 

 are obtuse or acute rhomboids, or long quadrilateral 

 tables : cleavage is parallel to all the planes of an 

 obtuse rhomboid of 106 30' ; lustre between vitre- 

 ous and resinous. It is more or less transparent, 

 commonly of a grayish or yellowish-white colour, 

 with some shade of green or brown ; hardness equal 

 to apatite; specific gravity 4-1 to 44. It is com- 

 posed of oxide of zinc 65-2 and carbonic acid 34-8. 

 Before the blow-pipe, it is infusible, but loses about 

 thirty-four per cent, by ignition. It dissolves with 

 effervescence in muriatic acid. It is very abundant 

 in England, in Siberia, and in several countries of 

 Europe. It is an ore which is highly prized, on ac- 

 count of the facility with which brass may be manu- 

 factured from it. 



5. White vitriol occurs massive, stalactitic, bo- 

 tryoidal, reniform, and investing. The structure 

 of the massive is fibrous and radiated. It is shining, 

 soft, brittle and translucent ; specific gravity 2. It 

 has a nauseous and metallic taste. It consists of 



Oxide of zinc, 

 Sulphuric arid, 

 Oxide of many-anose, 

 Water, . 



27-5 



22-0 



05 



50-0 



Before the blow-pipe, it is fusible with ebullition, 

 giving off large quantities of sulphureous acid, and 

 leaving a gray scoria. It dissolves in boiling water. 

 It occurs principally with blende, from whose de- 

 composition it is supposed to arise. Its localities 

 are England, the Hartz, Austria, and Sweden. 



The ores of zinc are met with in Germany, Bel- 

 gium, France, and Sweden ; and in Great Britain, 

 in Cornwall, especially in Huel Hope mine, in the 

 parish of Gwennap ; in a conglomerate or pudding- 

 stone-rock of the Mendip Hills in Somersetshire; 

 abundantly in the limestone of Derbyshire, where 

 the lead-mines are situated ; and associated with 

 the lead-ore at Holywell in Flintshire ; at Aldstone 

 Moor in Cumberland ; and at Wanlock Head and 

 Lead-Hills on the borders of the counties of Dum- 

 fries and Lanark. But all the zinc that is now 

 produced in the United Kingdom is trifling in 

 quantity, and quite insufficient for the demand, so 

 that a large amount is imported annually, chiefly 

 from Germany and Belgium. In the year 1833 the 

 importation was 65,115 cwts., of which rather more 

 than a half was retained for home consumption, the 

 chief export being to the East Indies. 



To obtain the metal, the ore, whether it be ca- 

 lamine or blende, after being raised from the mine, 

 is carefully picked, to separate any impurities, and 

 roasted in a furnace in a moderately red heat, by 

 which the carbonic acid is driven off from the cala- 

 mine and the sulphur from the blende. An oxide 

 of zinc remains, and this is intimately mixed with 

 powdered coal by their being ground together in a 

 mill. The mixture is now put into large earthen 

 crucibles, about four feet high, having an iron tube 

 in the interior, one end of which rises near to the top, 

 the other passing through the bottom of the jar and 

 the floor of the furnace into a cistern of water un- 

 derneath. Covers are firmly luted to the crucibles ; 

 they are surrounded with fuel in the furnace, and 

 an intense heat is kept up for several hours. The 

 carbon of the coal combines with the oxygen of the 



