USEFUL METAL* 191 



Stivnsthrup found native iron disseminated in large I KM lies of 

 basalt in situ, and considered it a part of the rock itself. Two 

 questions have arisen concerning its origin : (1) Wasitpn -i-nt in 

 the original magma as metallic iron? (2) Was it reduced l>y 

 carbonaceous matter in its upward transition through the earths 

 crust? 



F. W. Clarke states that the iron may have come as such from 

 great depths below the surface to teach us that the earth is essen- 

 tially a vast meteorite and that its interior is rich in uncoml)in d 

 metals. 



According to A. Daubre"e the latter supposition is admissable 

 for he prepared artificially pellets of metallic iron containing 

 nickel almost identical in composition with the specimens of 

 native iron from Disco Island, Greenland. 



According to C. A. Young, from 20,000,000 to 24,000,000 

 meteorites fall through the atmosphere of the earth every 24 

 hours. These particles blacken the snow and the ice of the perma- 

 nent snow fields, sink to the bottom of the ocean, or mingle with 

 the soil of the locality in which they happen to reach the earth. 



Troilite, the ferrous sulphide, FeS, is common in iron meteor- 

 ites in nodules disseminated more or less sparingly through the 

 mass. It also occurs in narrow veins usually separated from 

 the iron by a thin layer of graphite. 



Pyrite and pyrrhotite occur as primary minerals as minor ac- 

 cessories in the igneous rocks. The former appears in both the 

 acid and the basic intrusives, while pyrrhotite is more character- 

 istic of the ferromagnesian varieties, as diabase and diorite. 

 They have both been observed as sublimation products from 

 volcanoes. 



According to F. W. Clarke, dry gases, wet gases, and alkaline 

 solutions charged with hydrogen sulphide are capable of producing 

 these minerals. The magmas contain the reagents and the re- 

 actions naturally follow. 



According to J. H. L. Vogt, these sulphides are actually solu- 

 ble in silicate magmas, especially at high temperatures, and are 

 among the first minerals to crystallize. Vogt regards certain 

 of the pyrrhotite deposits of Norway as the direct product- of 

 magmatic segregation. 



Marcasite, the orthorhombic sulphide, FeSj, is common in 

 metalliferous veins and in the sedimentary rocks, but its origin 

 is unknown. 



