IRON ORES. 63 



H. 3-5; S.G. 4-4 to 4-6. 



Composition about 60 per cent, iron, the rest sulphur. 



In the outer B.F. on charcoal, a red oxide of iron globule 

 is formed ; in the inner flame, fuses and yields a black mag- 

 netic globule having a yellowish fracture. It is not so hard 

 as iron pyrites, and is slightly attracted by the magnet. 



Arsenical Pyrites (mispickel : often called mundic by 

 miners in Cornwall and Devonshire). 



Crystallization rhombic prisms modified on the angles, 



/fee. 



Colour silver white. 

 Streak greyish black. 

 Lustre shining. 

 H. 5-5 to 6; S.G. 6-3. 

 Composition about 35 per cent, iron, the rest arsenic 



and sulphur ; cobalt sometimes occurs in the ore. 



Before B.F. a magnetic globule is obtained, and a smell of 

 garlic noticed. Strikes fire with steel, and a decided odour 

 of garlic noticed. Heated in a tube a sublimate is obtained. 



Specular Iron (hcematite). 



Crystallization rhombohedral ; some crystals are thin 



hexagonal tables with oblique edges. 

 Colour dark steel grey in some varieties, but red in 



some earthy ones. 



Streak powder invariably dark cherry red. 

 H. 5-5; S.G. 4-5 to 5-3. 

 Composition 70 per cent, iron, the rest oxygen. 



Infusible before B.F., but with borax gives a yellow glass 

 in the outer flame, a green glass in the inner flame. 



Varieties of this ore are : 



Specular iron of a metallic lustre. 



Red haematite an opaque mineral, not of a metallic lustre, 

 brownish or red in colour. Has a radiated structure. 

 ' Eed ochre and red chalk soft and earthy, generally con- 

 taining a quantity of clay. 



