369 
1909-10.] The Chemistry of Submarine Clauconite. 
case, some colour is lent to the hypothesis long ago thrown out as a mere 
suggestion by Julien,* * * § that humus acids play a part in the formation of 
glauconite ; in agreement with which view is the fact that the characteristic 
occurrences of glauconite are not in the deep sea but rather at no great 
distance from the shore-line. 
There is a further consideration which seems to bear on this point. 
According to Murray and Renard,f granular glauconite is formed from 
casts or moulds, within foraminifera shells, of infiltrated clayey silt. The 
principal changes involved in the transition from clay to glauconite are 
removal of alumina and silica and attachment of potash. It has been 
pointed out, however, by Leith, | that in order to form the highly ferruginous 
glauconite far more iron than was originally contained in a clay cast must 
have been imported from outside. Since there are 5-10 per cent, of Fe 2 0 3 
in submarine mud, and 20-30 per cent, of glauconite, and since a ballast of 
10-15 per cent, of alumina has to be eliminated, not to mention silica, it 
must be admitted that the production of glauconite casts from clay in 
situ seems an uphill process. Such a process would be greatly facilitated 
if a substance having a specific solvent and therefore concentrative 
power for iron ( e.g . humic acid) were at hand. Putting together, then, 
the existence of humus-like carbonaceous matter within glauconite grains, 
the presence, frequently reported, of vegetable refuse § in greensand 
deposits, and the well-known solvent power of humic acid for iron, the 
participation of decaying vegetable matter in the formation of glauconite, 
whether we start from clay casts or not, appears far from improbable ; 
but it is impossible to suggest a precise rationale with the knowledge 
so far at disposal, the more so since in all likelihood bacterial activity is 
involved. 
Collet and Lee draw attention to the absence of glauconite in lakes, and 
are disposed to account for it by the tendency of humic acid to keep iron 
and silica in solution. Where there is much dissolved humic acid, as in 
some lakes (by no means all, or even the majority), this solvent action may 
play a part in preventing the formation of glauconite ; but after all, the 
most potent reason for its absence would seem to be the scarcity of one 
of its essential constituents, namely potash. In ordinary lake-waters 
K 2 0 seldom exceeds 5 parts per million, whilst in sea-water there are 
about 400 parts per million. 
* Proc. Amer. Assoc., xxviii. p. 363, 1879. 
t Challenger Reports, “Deep-Sea Deposits,” p. 389, 1891. 
f Loc. cit., p. 254. 
§ Challenger Reports, “Deep-Sea Deposits,” p. 380 ; Murray and Lee, loc. cit., p. 20. 
