371 
1909-10.] The Chemistry of Submarine Glauconite. 
properties throw any direct light on the glauconite problem, evidence is now 
at hand that when ferric oxide held in solution by an organic acid acts on 
a hydrosol of silica in presence of potash (which may well be what occurs 
when glauconite is formed), a green potassic ferroso-ferric silicate is, under 
suitable conditions, produced. F urther, since the green colour of the artificial 
silicate is bound up with the presence of ferrous iron it seems likely that the 
same may hold good for natural glauconite ; nevertheless, experiments made 
with the aim of “ bleaching ” the latter by oxidising agents proved unsuccess- 
ful, because it does not readily enter into reaction wfith aqueous solutions. 
IV. The State of Aggregation of Glauconite. 
Owing to the birefringence and pleochroism exhibited by submarine 
glauconite when examined under the microscope, it has hitherto been usual 
to regard glauconite as a crystalline mineral; indeed Collet and Lee 
definitely relegate it to the monoclinic system.* Against this we have to 
set the fact that in the submarine mineral, whether granular or pulveru- 
lent, nothing in the least like a crystal-contour has ever been noted. It is 
true that fossil “glauconites,” embedded in continental formations, have 
been from time to time described, which are morphologically as well as 
optically crystalline. These, however, cannot be accepted as identical with 
recent submarine glauconite, though they may perhaps be metamorphic 
derivatives of it ; in the absence of analyses it is not unlawful to suspect 
that some of them may be a quite distinct mineral, possibly chlorite. 
On the other hand, certain properties of glauconite indicating a state 
of aggregation differing from that of ordinary crystalline minerals have 
been referred to above. Some additional light is shed on this point by 
the behaviour of glauconite as regards hydration. It is a peculiarity of 
colloid minerals (e.g. clays) and of zeolites that they absorb somewhat large 
proportions of water, according to the moistness of the air with which they 
are in contact, without forming definite hydrates. In order to ascertain 
whether glauconite falls into this class, a series of experiments was made 
according to the method first described by Van Bemmelen j* and extended 
to minerals by Tammann j and Lowenstein.§ Purified Albatross glauconite, 
prepared as on p. 364, was spread in fine powder on glass dishes, which 
were suspended in closed jars over sulphuric acid of various concentrations ; 
that is, they were exposed to various tensions of aqueous vapour. The jars 
were left in a cellar, at a temperature ranging from 9° to 11°, for eight 
months, after which equilibrium was thoroughly established. A specimen 
* Loc. Git., p. 243. t Zeitschr. anorg. Chem., xiii. p. 231, 1897. 
1 Zeitschr. f. phys. Ghent., xxvii. p. 323, 1898. § Zeitschr. anorg. Ghent., lxiii. p. 691, 1909. 
