191Jf^] Certain Mineral Kesources 23 



condition. Again, there would be a somewhat gradual passage 

 from the chromite to the pure peridotite. 



In prospecting for either chromite or corundum the largest 

 and richest deposits may be expected near the contact of the 

 peridotite with the gneiss or other country rock. 



Chromite has been found only in peridotite and serpentine, 

 and the presence of this mineral in these rocks would at once 

 indicate that the rocks were of igneous origin. 



The large deposits of chromite in the serpentine rocks of 

 Pennsylvania and Maryland show that the primary rock was of 

 igneous origin and that the mineral solidified out from the 

 molten magma, as described above. 



A natural corollary to be drawn from this proposition is that 

 the occurrence of chromite in an alluvial deposit indicates the 

 proximity of a peridotite rock of igneous origin, which was the 

 original source of the chromite. 



The association of platinum with chromite and serpentine, 

 in various parts of the world where platinum has been found in 

 alluvial deposits, indicates that the origin of the platinum is a 

 peridotite or allied rock of igneous origin. On the eastern slope 

 of the Urals platinum has been found associated with chromite, 

 which is disseminated through an olivine rock. It is not un- 

 reasonable to suppose that platinum would be found in the per- 

 idotite areas of the Southern States. 



The mining of chromite in this country has always been at- 

 tended with considerable uncertainty on account of the pockety 

 nature of the deposits, and for this reason chromite properties 

 are more apt to be leased than bought outright. Usually no 

 estimate can be made regarding the amount of chromite on a 

 property beyond that which is exposed by the actual work done. 

 Yet, considering the theory advanced for the origin of chromite, 

 if a deposit of this mineral is found near the contact of the 

 peridotite and other country rocks, and if this peridotite forma- 

 tion is very extensive and the chromite is found in considerable 

 quantity, there is good probability that it will develop into a 

 large deposit. 



Maryland was one of the first states in which chromite was 



