HISTORY OF CRYSTALLINE ROCKS. 11 
§ 11. Their variations show that the material in question is a mixture, and render it 
difficult to fix its real constitution. According to the multiplied analyses of Haushofer, 
the iron present in glauconite is for the most part in the ferric condition, the ferrous oxyd 
in yarious examples ranging from three to seven hundredths. The formula proposed by 
him represents glauconite as containing 6.3 of ferrous oxyd, 8.3 of potash, and 9,6 of water, 
with 22.7 of ferric oxyd and 3.6 of alumina, giving for the atomic ratios of protoxyds, ses- 
quioxids, silica, and water, 1: 3: 9: 3! The very variable quantity of alumina found in 
glauconites may, however, well be owing to a zeolitic admixture; and if we hazard the 
conjecture that the large proportion of ferric oxyd therein is due to a partial oxydation of 
what was originally a ferro-potassic silicate, we should have for its composition before 
peroxydation (deducting the alumina as a zeolite with the above atomic ratios, like faujas- 
ite) a silicate with the ratios for protoxyds, silica, and water, of 8: 9: 8, corresponding 
to sepiolite and to an unknown pectolitic silicate intermediate between pectolite and 
apophyllite, which may be supposed to have given rise alike to talc, to sepiolite, and 
to glauconite. The variable amounts of magnesia in glauconite itself would thus be due 
to an admixture of sepiolite. The reaction of such a soluble pectolitic compound, having 
a lime-potash base like apophyllite, with the dissolved magnesian salts in sea-water 
would generate a magnesian silicate having the ratio of talc and sepiolite (which latter 
forms beds in Tertiary sediments), and with ferrous solutions, by a similar double decompo- 
sition, might yield a ferro-potassic silicate like glauconite. It is well known that, under 
proper conditions, decaying organic matters acting upon sediments containing ferric oxyd 
reduce this and give rise to such solutions, in which ferrous carbonate is often associated 
with a proportion of an organic acid. Such a process of solution and redeposition in forms 
of siderite and pyrites goes on in sedimentary deposits through this agency. This would 
permit the conditions necessary to produce glauconite with the pectolitic silicate, which in 
the absence of the iron-solution would generate sepiolite by reaction with magnesian salts. 
$ 12. The variations in the composition of glauconite-like minerals, and the existence 
in silicates similar to it in their mode of occurrence, of more or less alumina and magnesia, 
probably corresponding, as suggested above, to admixtures of zeolite and sepiolite, are 
farther illustrated by the following analyses by the writer. I is a typical glauconite from 
the green-sand beds of the cretaceous series in New Jersey ; II, a glauconite, remarkable for 
its fine green colour, which forms layers in the Cambrian (Potsdam) sandstone at Red Bird, 
Minnesota; III, a similar material found in a Cambrian sandstone on the island of Orleans, 
near Quebec. The results, after deducting siliceous sand, are calculated for one hundred 
parts, and the whole of the iron is represented as ferrous.’ 



I. Il. III. 
SHIlGS, round amannos 50.70 46.58 50.7 
Ferrous oxyd..-......... 22.50 20.61 8.6 
Maonesia ceboonenagadce 2.16 1.27 Sail 
Ibis, ooc 0 bad dE onde sta 2.49 — 
INinrauntomdodeomodeooons 8.03 11.45 19.8 
POTASH cceccc cecscncece ss 5:80 6.96 8.2 
Od aetateletetclotselericisieteiere versie O7. 0.98 0.5 
WEétoantosc son uses 8.95 9.66 8.5 
100.00 100 00 100.00 

! Cited in Dana’s System of Mineralogy, 5th ed., p. 462. 
* Geology of Canada in 1863, p. 486: also Rep. Geol. Surv. of Canada 1863-69, p. 232. 
