ZINC 1187 



ZAFFKE. See COBALT. 



ZEA* Indian corn or maize is obtained from an American grass, the Z.ea mays. 

 It is now largely cultivated in the East Indies and in Northern Africa, and is grown 

 to some extent in the south of Europe. 'Popped corn' is prepared by heating the 

 grains on a hot metal plate, when they open and expose their starchy contents ; sweet- 

 ened and coloured, they form a sweetmeat known as ' corn ball.' 



ZEDOARY. (Zedoaire, Fr. ; Zittwer, Ger.) The root of a cucurbitaceous plant 

 imported from Ceylon, Malabar, and Cochin-China, employed sometimes medicinally, 

 It occurs in wrinkled pieces, externally ash-coloured, internally brownish-red ; possessed 

 of a fragrant odour, and of a pungent, aromatic, bitterish taste. 



ZEOLITES. A group of minerals consisting of hydrous silicates of alumina and 

 other bases. They gelatinise with acids, and intumesce when heated, whence their 

 name (C, ze,o, to boil). They are found in the cavities of amygdaloi'dal rocks, and a 

 few also occur in mineral veins. None of them is of any use in the arts. 



ZINC (Atomic weight, 32-5 ; symbol, Zn) is a metal of a bluish-white colour, of 

 considerable lustre when broken, but easily tarnished by the air ; its fracture is hackly, 

 and foliated with small facets, irregularly set. It has little cohesion, and breaks in 

 thin plates before the hammer, unless it nas been previously subjected to a process of 

 lamination, at the temperature of from 220 to 300 Fahr., by which it becomes 

 malleable and ductile. On this singular property a patent was taken out by Messrs-. 

 Hobson and Sylvester, of Sheffield, many years ago, for manufacturing sheet zinc for 

 covering the roofs of houses, and sheathing ships ; but the low price of copper at that 

 time, and its superior tenacity, rendered their patent ineffective. The specific gravity 

 of zinc varies from 6 - 9 to 7'2, according to the degree of condensation to which it has 

 been subjected. It melts under a red heat, at 773 Fahr. When strongly heated 

 with contact of air, the metal takes fire, and burns with a brilliant bluish-white light, 

 while a few flocculi of a woolly- looking white matter (nil album') rise out of the cru- 

 cible and float in tho air. The result of this combustion is a white powder, formerly 

 called ' flowers,' but now oxide of zinc. 



The principal ores of zinc are, the sulphide called blende, the carbonate called cola- 

 mine, and the silicates of zinc. 



1. Blende crystallises in rhombic dodecahedrons ; its fracture is highly conchoidal ; 

 lustre, adamantine; colours, black, brown, red, yellow, and green; transparent or 

 translucent ; spec. grav. 4. It is a simple sulphide of the metal (ZnS) ; and, therefore, 

 consists in its pure state, of 32'5 of zinc and 16 of sulphur. It dissolves in nitric acid, 

 with disengagement of sulphuretted hydrogen gas. It occurs in beds and veins, ac- 

 companied chiefly by galena, iron pyrites, copper pyrites, and heavy spar. There is 

 a radiated variety found at Przibram, remarkable for containing a large proportion of 

 cadmium. Blende is found in great quantities in Derbyshire and Cumberland, as also 

 in Cornwall and many other localities. It is frequently termed ' black jack.' 



2. Calamine is a mineral occurring usually in concretionary forms and compact 

 masses, yellowish -white when piire, biit frequently brown through the presence of iron. 

 It crystallises in rhombohedra, and has a spec. grav. of about 4'4. It is a normal 

 carbonate of zinc (ZnO.CO- = ZnCO 3 ) containing, when pure, about 52 per cent, of 

 zinc. It is an abundant ore in Derbyshire, Cumberland, Belgium, Sardinia, Silesia, 

 &c. The carbonate is termed by some writers Smithsonite, a name applied by others 

 to the hydrous silicate. See CALAMINE. 



3. Smithsonite or Electric calamine is an ore occurring in compact masses, and in 

 mammillated, botryo'idal, and fibrous forms. It is found in Carinthia, Hungary. 

 Belgium, New Jersey, &c. It is a hydrous silicate, containing 2ZnO.SiO- -t- HO 

 (Zn-SiO 4 + H 2 O). Many writers term this ore calamine. 



4. Willcmitc. An anhydrous silicate of zinc, containing 2ZnO.Si0 2 (Zn 2 SiO' 1 ). It 

 is found at Vieille Montague, near Aix-la-Chapelle, and at Franklin and Stirling, in 

 New Jersey. 



5. Zincitc, Spartalite, or "Reel sine ore occurs at Mine Hill and Sterling Hill in New 

 Jersey, where it is associated with franklinite. It is an oxide of zinc (ZnO) containing 

 a little oxide of manganese. An artificial oxide of zinc is sometimes found crystallised 

 among blast-furnace products. 



The zinc ores of England, like those of Franco, Belgium, and Silesia, occur in two 

 geological positions. The first is in the carboniferous or mountain limestone. The 

 blende and the calamine most usually accompany the veins of galena which traverse 

 that limestone ; though there are many lead mines that yield no calamine ; and, on the 

 other hand, there are veins of calamine alone, as at Matlpck. 



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