283 



Variegated like a pidgeons neck, and is not 

 eafily altered by expofure to the air. Its form 

 either -granular, cufpidated, cuneiform, prif- 

 rnatic or rhomboidal. It is magnetic neither 

 before nor after calcination, is foluble in acids, 

 affords arfenic by diftillation, in the propor- 

 tion of 30 or 40 per cent, and fometimes con-* 

 tains a fmall proportion of copper and filver, 

 It is frequently mixed with other metallic ores, 

 and often found in indurated clay, quartz, 

 fpar, fhoerl, &c. 



34. When iron contains lefs than T '^ of arfe- 

 nic, it is magnetic, Scheff. . 300, therefore if 

 the calcination be puftied fo far, the iron will 

 remain magnetic. It may be analyfed by 

 folution in the marine acid, which will take 

 up the iron and leave the arfenic, or by fo- 

 lution in aqua regia, which will take up 

 both, but water being added, will precipitate 

 the arfenic and leave the iron. The iilver 

 will remain in the form of horn filver, and 

 the copper may be feparated by the methods 

 already mentioned.' 



SPECIES XXL 



/ 



Combujllble Iron Ore. 



i 



35. Of this kind Mr. Cronjled mentions 

 two varieties, one, of which the greater part 



is 



