THE KEWEENAWAN. 421 



rich enough for mining have been received. A determination of the nickel in iron 

 ore from the locality of the specimens above analyzed showed less than one-half of 

 one per cent." 



Tlie iron-oxide bodies occur in the midst of massive granular normal 

 gabbros, and are not separated from the gabbro by sharp lines. The titan- 

 iferous magnetite body on the margin of any outcrop next the gabbro is 

 lean, and has a large proportion of pyroxene, olivine, and feldspar, in 

 general of gabbro minerals, mixed with the titaniferous magnetite. These 

 minerals become fewer toward the main magnetite mass, but in the direction 

 of the gabbro they increase in quantity, first giving varieties of highly 

 magnetitic gabbro, but gradually passing into the crystalline gabbro, with 

 black and gray mottlings. There is then a transition from the gabbro into 

 the titaniferous magnetite bodies, which are but very magnetitic portions of 

 the gabbro. 



The high percentage of titanium in the magnetite bodies, as shown by 

 the above analyses, is very important from both the economic and the 

 scientific standpoint. In the first place, the titanium renders the magnetite 

 at present valueless, since, in the present iron-smelting practice, titaniferous 

 ore can not be smelted economically. The magnetites can, therefore, not 

 compete now with the cheap non titaniferous ores, nor can they in the 

 future, unless new discoveries give a higher value to titaniferous ores, or 

 cause changes in iron smelting which will place the titaniferous ores on an 

 even basis witli the other iron ores. 



The injuiious eifect of the titanium in rendering the magnetite unmar- 

 ketable would, of course, apply to these titaniferous magnetite bodies, what- 

 ever their size. However, so far as we know, up to the present time no 

 pi;blished description has been given of any large continuous masses of the 

 practically pure titaniferous magnetite. 



The content of titanium is of interest from a scientific standpoint, in that 

 it gives evidence (additional to that off'ered by the occurrence) of the intimate 

 connection between the gabbro and the ore, and enables us to determine its 

 source. The gabbro contains everywhere titaniferous magnetite in small 

 quantities, and the large amount collected in these magnetite bodies owes 

 its accumulation to those little understood processes generally spoken of as 

 processes of segregation. As the result of these processes the titaniferous 



aLoc. cit., p. 62. 



