THE RARE METALS 273 



Nigrint , TiOj, is a black variety, containing from 2 to 3 per 

 cent, of Fe 2 O 3 . 



llm> minitile is a black variety from the Ilmen Mountains, 

 containing 10 per cent, or more of Fe 2 O 3 . It carries too 

 much iron to be classified as rutile, and too much titanium for 

 ilnicnite. 



Octahedrite, TiO2, occurs in definite octahedrons of the tetrag- 

 onal system. 



Brookite, TiO 2 , crystallizes in the orthorhombic system. 



Perovskite, CaO,TiO 2 , is a calcium titanate. 



Titanite, CaO,TiO 2 ,SiO 2 , often called sphene, on account of its 

 wedge-shaped crystals. 



The oxide, Ti 2 0s, has not been observed as an independent 

 mineral. 



Origin of the Ores. Ilmenite is widely diffused throughout 

 both the acid and the basic intrusives, and on account of its 

 basicity is one of the earliest minerals to segregate from a cooling 

 magma. Leucoxane is always secondary in origin. Rutile is a 

 common constituent of the acid intrusives, and is occasionally 

 found in limestones, dolomites and slates. The variety octahe- 

 drite is always of secondary origin. Perovskite is associated with 

 both eruptive and metamorphic rocks. Titanite is a pyrogenic 

 mineral in the older secretions of the acid intrusives, as granites, 

 syenites, etc. 



Character of the Ore Bodies. The titaniferous iron ores occur 

 in considerable quantities in the State of New York. They are 

 mined chiefly for their iron content, and occur in more or less 

 lens-shaped masses. Titaniferous magnetite is a common mineral 

 in New York and New England. In Nelson County, Va., large 

 dikes of pegmatite, sometimes hundreds of feet thick, cut a 

 biotite gneiss. Rutile and ilmenite occur in these dikes, asso- 

 ciated with the potassium and sodium feldspars, amphibole, 

 hornblende, quartz and apatite. In the pegmatite itself, the 

 titanium ores are not sufficiently abundant to become a commer- 

 cial consideration; but the pegmatites are cut by veins or dikes of 

 rutile, ilmenorutile, and apatite, which F. L. Hess considers as a 

 later phase of the pegmatites. At Roseland, Virginia, in the same 

 county, the rutile comprises about 4 per cent, of the pegmatite. 

 The rock is crushed and concentrated together with the decompo- 

 sition-products that overlie the pegmatite, to a product containing 

 approximately 98 per cent. TiO 2 . 



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