62 JOHN BIRKINBINE 



mines in recent years. Large stocks of ore accumulated at 

 or near blast furnace plants aided in swelling the total iron 

 ore supply to figm'es never before reached. 



Iron ore may be considered in four general commercial 

 classes, as follows : 



(1) Red hematite, including all anhydrous hematites, 

 known by various names, such as red hematite, specular, 

 micaceous, fossil or slate iron ore, martite, blue hematite, etc. 



(2) Brown hematite, including the varieties of hy- 

 drated sesquioxide of iron, recognized as limonite, goethite, 

 turgite, bog ores, pipe ores, etc. 



(3) Magnetite, an ore in which the iron occurs as mag- 

 netic wside and which includes some martite, mined with 

 the magnetite. Martite is a red hematite ore which preserves 

 to a varying extent the crystalline form of magnetite, but 

 which is nonmagnetic, or nearly so. 



(4) C&.rbonates comprise those ores which contain a 

 considerable amount of carbonic acid, such as spathic ore, 

 blackband, siderite, clay ironstone, etc. 



This classification is to be considered as general, the ores 

 having various local or trade names. Thus the prevailing 

 color or general physical appearance is used to indicate an ore, 

 as blue, black, red, or brown, micaceous or glistenmg hema- 

 tite. The term specular, although more properly applied 

 to a glistening ore, is by custom given to many dull red hema- 

 tites. Other hematites receive designations according to 

 their topographical or geographical occurrence, as fossil, 

 mountain, or valley ore, or to the structure, as flaxseed ore, 

 slate ore, etc. In the brown hematite class limonite, turgite, 

 etc., are mineralogical terms referring to the degree of hydra- 

 tion, but the physical structure and appearance of some of 

 the ores are described by the term lump ore, pipe ore, botrj^- 

 oidal ore, needle ore, etc., The beneficiating of brown hema- 

 tites has given rise to the terms wash ore, sand ore, etc. The 

 carbonate ores are known as spathic ore, limestone ore, black- 

 band ore, kidney ore, etc. 



The association of other substances with iron also fur- 

 nishes names to certain ores, such as pyrite, pyrrhotite, il- 

 menite, chromite, etc., but in this discussion it is not essen- 



