296 Chemical Origin of Iron Ores, Etc. — Winchell. 
white and translucent silica is duly considered, and it is com- 
pared with the known product of chemical precipitation from 
siliceous waters, the idea of chemical precipitation is forcibly 
presented as the possible origin for the chalcedonic silica of 
the jaspilyte. There is no way known in nature for the for- 
mation of chalcedonic silica except chemical deposition. The 
different bands of the jaspilyte, varying in color from white to 
red, brown and sometimes nearly black, are all formed by the 
varying proportions of hematite and silica. Ordinary sedi- 
mentary action could not select from the products of erosion 
simply two substances and unite them in characteristic strata, 
when the ocean's waters must have been heavy with suspended 
matter of many different kinds. Some selective, discrimi- 
nating force was at work which was able to abstract silica, or 
silica and iron oxide, from the water, and reject all the rest. 
In the light of what has already been said regarding the 
nature of the schists enclosing the ore masses, it is plain that 
the waters of the Keewatin ocean were constantly agitated by 
volcanic eruptions. It is also plain that they must have been 
hot, and in some places, or after irregular intervals of time, 
they must have been probably evaporated, and at other times 
suddenly cooled. The earth's crust was thin and easily rent, 
and the contact of water and molten rock was frequent. The 
waters became alkaline by solution, from the lavas, of the mag- 
nesia, potash and soda, and other alkaline elements. In this 
condition it would also become surcharged with soluble silica 
and iron, obtaining the latter from the augitic minerals of the 
basic lavas, and possibly from masses of erupted metallic iron. 
Indeed the ocean was a hot, compound decoction of all the 
minerals that could be dissolved from the eruptive diabases ; 
and of those minerals there was no exception. 
Under such circumstances it requires no extensive research 
nor chemical foreknowledge to predict what would be the 
result whenever the equilibrium of super-heated and super- 
saturated oceanic water was disturbed. Something would be 
precipitated. Would it be silica and ferric oxide? 
On this point Hunt says : '^ "The atmosphere, charged with 
acid gases which surrounded this primitive rock, must have 
" T. Sterry Hunt, The chemistry of the primeval earth, Am. Jour. Set. 
Jan. 1858. Smithsonian Report, 1869, p. 189. Chemical and Geological 
Essays, 1878, p. 40. 
