BLENDE 



397 



off. It is said that 4,000 fish are necessary for the production of a pound of scales, 

 for which the fishermen of the Chalonnois get from 18 to 25 livres. 



The poarl essence is obtained merely by well washing the scales which have been 

 scraped from the fish in water, so as to free them from the blood and mucilaginous 

 matter of the fish. See PEABLS, ARTIFICIAL. 



BXiEWDE, from Slendcn, Ger., to dazzle. Sulphide or sulphuret of zinc is a com- 

 mon ore of zinc, composed of zinc 67, sulphur 33 ; but it usually contains a certain 

 proportion of the sulphide of iron, which imparts to it a dark colour, whence the name 

 of ' Black Jack,' applied to it by the Cornish miner. The ore of this country gene- 

 rally consists of ziuc 61'5, iron 4'0, sulphur 33'0. Blende occurs either in a botryoidal 

 form or in crystals (often of very complex forms), belonging to the tetrahedal division 

 of the cubic or monometric system. H = 3'5 to 4. Specific gravity = 3'9 to 4. See 

 Zixc. H.W.B. 



In gome districts the presence of the sulphide of zinc is regarded by the minors as 

 a favourable indication, hence wo have the phrase, ' Slack Jack rides a good horse.' 

 In other localities it is thought to be equally unfavourable, and the miners say, 

 'Slack Jack cuts out the ore' For many years the English zinc ores were of little 

 value, the immense quantity of zinc manufactured by the Vieillo Montagne Company, 

 and sent into this country, being quite sufficient to meet the demand. Beyond this, 

 there was some difficulty in obtaining zinc which would roll into sheets, from English 

 sulphides. 



Much of the zinc obtained from blende is used in the manufacture of brass. 



Pure blende is a mineralogical rarity ; the white and colourless variety (Cleiophane) 

 of New Jersey, United States, was analysed by the late T. H. Henry, and found to 

 be absolutely pure, with the exception of a trace of cadmium. Blende nearly always 

 contains sulphide of iron. The following analyses of varieties of blende illustrate 

 this : Sulphide Sulphide 



of Zinc of Iron 



Charente 82-76 1371 



English 91-8 6'4 



Production of Zinc Ore in the United Kingdom in the years 1870 and 1871, showing 

 the produce of each district. 



Metallic zinc produced, 1870, 3,936 tons ; 1871, 4,966 tons. 



Year 



1870 Zinc or Spelter 



1871 Crude Zinc 



IMPORTS. 



Tons Tons Tons 



28,775 Zinc Ore 44,553 Oxide of Zinc 2,328 



20,929 Ditto 29,418 Manufactured 8,765 



EXPOETS. 



1870 Zinc.British & Foreign 10,331 ... ... Oxide of Zinc 1,385 



1871 Ditto ditto 6,452 Zinc ore 184 



In 13 out of 16 analyses of blende from different localities recorded by Rammcls- 

 berg, iron is present in proportions varying from 1'18 to 18'1 per cent. Copperocca- 

 sionally occurs in blende, but rarely above 1 per cent. Cadmium is a frequent, if not 



