The Indiana State sentinel. [volume] (Indianapolis) 1868-1895, 1877-01-17
NATURAL HISTORY LYCEUM.
A Paper On the Origin In Nature of Hy-
drafted Brown Oxide Of Iron.

The following paper on the origin of ores
of hydrated brown oxide OF iron or limon-
lite. the most abundant ore of iron in this
state, was read by professor e. 7. Cox, state
geologist before the Indianapolis Lyceum
of Natural History, at a recent meeting:
l desire briefly to call the attention of the
lyceum to the usual conditions under which
hvdrated brown oxide of iron is found in
Indiana. Illinois and western Kentucky,
especially the localities bordering the Cum
berland river in the latter state. GeolOg-
ically the ore lies at the base of the
pebbly sandstone or milestone grit of the
coal measures. and Immediately on the sub
carboniferous limestone. 1t is never found
in true veins or in continuous
seams, but in pockets, as large, ir-
regular shaped masses, which, with the
accompanying clay, usually hll cavities In
the limestone The source of this iron and
clay is to be looked for in chalybeate waters
highly charged with carbOnic acid and bicar-
Donate of lime. This carbonated mineral
water has the power to dissolve and decom-
pose rocks which il permeates OF over which
and through which it passes. The cement
ing constituents of sandstone are dissolved
out, leaving the grains of quartz in large
beds like those seen at New Providence.
where the sand is extensively mined for the
plate glass works of New Albany, Indiana,
and Louisville, Kentucky. At other lOcali-
ties the sand so formed has been mostly car
ried away by the mechanical moving force
of drainage waters. When in contact with
the limestone the mineral water has the
power of slowly dissolving the mass and form
ing cavities and channels through which 1t
finds its way to subordinate and imperviOus
beds; along these it flowed and found an ont
let into the surface drainage or descended
deep into the earth. BY contact with the
limestone and the air. which found ingress
into the cavities the iron which previously
existed as a carbonate of protoxide isfurther
oxidised and precipitated. The water also
loses probably by an interchange of con-
stituents, silicic acid and alumina. The latter
minerals constitute the substance of the
more or less ferruginous clay beds which
are ALWAYS found associated with the
hydrated brown hematites of the west.
The massive sandstone of the milestone
grit series sometimes resists the corroding
influences of the chalybeate water, but
Yields I'D a part of its silicic acid which is
replaced by ferric oxide, and the whole mass
within the influence of the water is meta
mOrphosed into a siliceous or avenaceOuS
iron ORE Then again small detached Jumps
of the original cOnglOmerate sandstone may
he seen lying here and there over the hills
and table lands in which the beds Of iron
ore are found, being the only representa-
tives of the massive sandrOck. which at one
of which is still seen in force on the sur
rounding high lands.
One of the most remarkable instances OF
the chemical effects produced by chalybeate
and carbonated water on rocks is to be seen
in Lawrence county, Ind. Here the sand
stone at the base of the coal measures is 100
fact thick quite feTIuginOus at the base
coarse grained and thickly set with small
quartz pebbles. Where undisturbed by
chemical action, il rests almost entirely
upon the Archimedes limestone. there being
only a few inches of intervening shale; but
where subjected to the action of chalybeate
and carbonated waters, the limestone has
been removed and its place is occupied by a
bed of white clay resting upon redish clay
that encloses, locally, beds of very pure
hydrated ferric oxide.
The entire bed of this clay varies from six
to ten feet in thickness. The greater part is
pure white or of pea green color. The
green color disappears when burnt and is
probably due TO organic matter or physical
structure. Distinct lamina may be seen H.
some of the masses: il contains no grit, and,
in every way studied, gives unmistakable
evidence of having been precipitated from
solution.
This clay differs essentially from kaolin,
both in the manner of its origin and in the
amount of water which it contains. In the
latter respect it resembles halloyste, but
differs from that mineral in not being so
translucent under any circumstances, and in
being highly plastic. To the touch some
specimens are unctious, others meager.
therefore have given TO il the name of Indi-
anaite. At some future time hope to pres
ent to the society paper especially devoted
TO these Lawrence county clay beds. Your
attention is merely called to them at this
time for the purpose of showing that the
formation of beds of ferric oxide and clay
are due to the chemical action of chalybeate
and carbonated waters on the rocks which
surround them; and that tie coal meas
ure eonglomerate is the chief source of the
iron and clay; that relatively pure hydrated
brown oxide of iron is always associated
with beds of clay, and that they lie in
cavities which have been excavated out of
the subcarboniferous limestone by the chem
jcal and mechanical action of mineral water.