184 



KEPORT OF NATIONAL MUSEUM, 1899. 



. Realgar is used mainly in pyrotechny, yielding a very bril- 

 liant white light when mixed with saltpeter and ignited. It is now 

 artificially prepared by fusing together sulphur and arsenious acid. 1 

 Orpiment is used in dyeing and in preparation of a paste for removing 

 hair from skins. According to the British consular reports there were 

 exported from Baghdan, in 1897, some 55,600 pounds of the mineral 

 for use as a pigment. As with realgar, the mineral is now largely 

 prepared artificially. The name "orpiment" is stated by Dana to be 

 a corruption of auripigment, golden paint, in allusion to the color. 



BIBLIOGRAPHY. 



W. I*. BLAKE. Occurrence of Realgar and Orpiment in Utah Territory. 



American Jourual of Science, XXI, 1881, p. 219. 



H. B. FULTON. Arsenic in Spanish Pyrites, and its elimination in the local treat- 

 ment for production of copper precipitate. 



Journal of the Society of Chemical Industry, V, 1886, p. 296. 

 Production of Arsenic in Cornwall and Devon. 



Engineering and Mining Journal, LII, 1891, p. 96. 

 WILLIAM THOMAS. Arsenic. 



The Mineral Industry, II, 1893, p. 25. 



3. COBALT MINERALS. 



Several minerals contain cobalt as one of their essential constituents 

 in sufficient quantity to make them of value as ores. In other cases 

 the cobalt exists in too small quantities to pay for working for this 

 substance alone, and it is obtained as a by-product during the process 

 of extraction of other metals, notably of nickel. The common cobalt- 

 bearing minerals, together with their chemical composition, mode of 

 occurrence, and other characteristics are given below : 



COBALTITE. Cobaltine, or cobalt glance. (Specimens Nos. 60922, 

 34266, U.S.N.M.) This is a sulpharsenide of cobalt of the formula Co 

 AsS, = Sulphur 19.3 per cent; arsenic, 45.2 per cent; cobalt, 35.5 per 

 cent; hardness 5.5, and specific gravity 6 to 6.3. The luster is metallic 

 and color silver white to reddish. When in crystals, commonly in 

 cubes or pyritohedrons. Analysis of a massive variety from I, Siegen, 

 Westphalia; II, Skutterud, Norway, and III and IV, Daschkessan, in 

 the government of Elizavetpol, Caucasus, as given by various author- 

 ities, yielded results as below: 



1 Wagner's Chemical Technology, p. 87. 



