These are very unusual deposits not found anywhere else on earth. The nitrate deposits are formed from water soluble saline minerals. It is the origin of these deposits which is not accounted for by present geological theories. The nitrogen occurs in a band 30km wide from Latt 19 deg 30 min S to 26 deg S, a distance of about 700km. Most of the deposits are at an altitude of over 1-2,000 meters and as high as 3 to 4,000 meters and involve an estimated 200,000,000 tons of nitrates. Sources of the following minerals are not clearly established
Chromium rich rocks are absent in Northern Chile and Chromium is rare in sea water.
Erickson was a senior geologist with the US.Geological Survey.
Erickson, George.E. "The Chilean Nitrate Deposits." American Scientist 71. 366-374.