214 ECONOMIC GEOLOGY 



most famous iron- ore deposits of the world. The iron ores occur 

 partly as segregations in the norite dikes and partly as veins, or 

 basic zones in the anorthosites. 



According to Thomas and MacAllister the iron ores in the 

 norite dikes at Storgangen consist of an intimate mixture of 

 ilmenite and hypersthene, together with a little labradorite. 

 The iron- ore deposits of Taberg, Sweden, are titaniferous and are 

 rich in olivine rather than hypersthene. The Taberg ores and 

 their associated gabbros are regarded as having their origin in 

 the same igneous reservoir. 



In the Ural Mountains there are several well known districts in 

 which iron-ore deposits are associated with porphyritic rocks. 

 The porphyries consist largely of orthoclase, plagioclase, augite, 

 sometimes with the original augite metamorphosed into horn- 

 blende. The segregations from these masses are largely mag- 



323 



FIG. 115. Section to illustrate the mode of occurrence of iron ores 

 in the Ekersund Soggendal district. (After Thomas and MacAlister's 

 Geology of Ore Deposits.) 



netites which occur as irregular patches and veins passing by 

 insensible gradations into the country rock. 



The iron ores of Lorraine and Luxemburg, Europe, have a 

 variable composition. The ores exist as oxides, including mag- 

 netites, also as carbonate and silicate. The ores are due in a 

 large measure to contemporaneous replacements and in part to 

 original depositions. 



The hematite deposits of southern Wales, Cumberland and 

 Lancashire occur in the Carboniferous limestones and may be 

 due to the leaching of iron compounds from the overlying Per- 

 mian terranes and the subsequent deposition of the iron ores by 

 metasomatic action. 



The iron ores from the Island of Elba, often beautifully crystal- 

 lized, have found their way into nearly all museums. Upon the 

 island there are four distinct districts: Rialtafio, Rio, Terra-Nova 

 and Calamita. Limonites and magnetites are present as well as 



