MINEUALOGy. 315 



Cobalt is not found pure ; its Ores being sometimes com- 

 bined with Arsenic and Sulphur, or Arsenic and Iron, and 

 accompanying the Ores of Copper, Silver, Arsenic, and Bis- 

 muth. It is brought to this country reduced to an Oxyde, of 

 a most brilliant blue colour, called Zaffre, which when melted 

 with three parts of Sand and one of Potash, forms blue glass ; 

 this reduced to a fine powder is known by the name of 

 Smalts, and is used for giving a blue tinge to various sub- 

 stances, as paper, cloth, linen, muslin, &c. ; likewise in 

 painting on porcelain, and also in oil and water. 



16. Manganese. Manganese is about seven times heavier 



than water ; its colour is a rusty grey ; it is brittle, 

 in a slight degree malleable, and is never found 

 pure. 



The Ores of this Metal are frequently met with in mineral 

 countries, and in a state of Oxyde is found combined with a 

 very considerable number of earthy and Mineral substances ; 

 the black Oxyde of Manganese affords all the Oxygen used 

 by the Chemist, and likewise the Oxygen in the composi- 

 tion of the Oxymuriatlc Acid, so essential to the bleacheries 

 of Europe. It is also used in glass making, and a beautiful 

 violet colour is obtained from it, which is employed in 

 painting porcelain. 



17. Tellurium. This is a rare Metal, it is about six times 



heavier than water j is very fusible, brittle, and of the 

 colour of tin. 



Tellurium is found in a Metallic state, but always alloyed 

 by some other Metal, as Gold, Lead, Copper, &c. 



