The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1890-10-22
AN lMpORTANTpAPER on IRON.
The Magnetization of Iron Ore
Considered.
"A Paper Read by MIR. Clemens Jones, of
Hohendauqua, Pa, Mt the Fall Meet
ing of the American Institute of Min
ing Engineers at New York September,
1890.

The peculiar property of the lode
stone has been known for many CEN
turtles. 1t was very early observed that,
by contact with it, iron is magnetized;
and it is needless to dwell here upon
the history allied to this discovery, now
constituting the wonderful science of
magnetism.
Deposits of magnetic ore are distribu-
ted all over the world. The ore is some
times very rich and comparatively free
from gangue, sometimes sparsely dis
seminatcd in the native rock. These
bodies of lean ore often cover large
areas. Modern ingenuity has utilized
the principle of the magnet, originally
derived from the ore itself, and really
belonging to the time of Plato and
Theophrastus, to separate the magnetic
ore particles from the rock which has
previously been crushed. This process
RECEIVERS the ore in the state of a con-
centrate very rich in iron and, in some
cases, desirable for Bessemer purposes.
The magnetic separator is no longer
novelty. 1t was only at the last meet
ing Of the Institute in New York, that
Messrs. Birkinbine and Edsion (Trans.,
xvii, 1881 and Mr.. Robert Cook Qb,
599) described some of the principal de-
signs of apparatus in use.
b. $. Dana Classics the natural mag
netic minerals in the following order:
magnetic, pyrrohotite, franklinite, al
mandite and minerals containing con-
siderable Eco" OF these, ferroso-ferric
oxide, or magnetic, is the type. The
proportionate amount of ferrous oxide
essential to magnetic the compound, is
not established. Ferrous oxide appears
to be tho only magnetic oxide of iron.
Tissandier, (Compt Rend., lxxiv. ,531)
produced ferrous oxide in the anhydrous
state by the action of carbon-dioxide on
pure iron at red heat, according to the
equation:
FetCOa=FeO+CO.
This is black, crystalline and mag
netic. Heated to redness in the air, it
is converted into Fe uO,.
Sidot (Compt. Rend., xvii, 1851 has
also produced an oxide exhibiting mag
netic polarity, by heating fcrric oxide TO
n temperature not sufficient to fuse it,
in an earthen tube placed in the mag
netic meridian.
a. Frcnzel (Jahrb. f. Min, 1874, D.
6s5) accidentally obtained small rhom-
bohedra, slightly magnetic, by igniting
precipitate of ferric hydrate.
The presence of ferrous oxide in mar
netite, whether us molecular constitu-
ent of the compound, or as an indepcnd-
ent molecule, seems to communicate the
property of magnetism.
Magnetic oxide Of iron, as an artificial
product, is considered to result from the
direct action of carbon dioxide. In
simple determinativc blow-pipe work
the reducingflame alone, or with the
aid Of alkaline carbonate, produces mag
netic particles. or slagglobules, from
nearly all iron-mincrals.
Spathic iron ores have long been
known to exhibit, after roasting, magnet
&c overwhelmingly due, however, to
the presence of metallic particles in the
roasted ore. Carbon dioxidc in the ore
is also here considered an important fac
tor. OF such ores, the orc-dressing at
the zinc works at Pribram, Bohemia,
described by Mr.. Ellis Clark, jr.. Grams,
tx, 45D, furnishes an illustration. The
principle is here used for the separation
of iron oxide from -blcnde.
"Thcse arc separated from othcr ma
terial by the ordinary concentration pro-
cesses, and are then in the form of
powder, the grains being less than
millimctcr in diameter. This powder
is composed of spathic iron-ore and zinc
blende, and is roasted i'll Il small oven,
with frequent stirring, for an hour,
when the ore is rendered sufficiently
IN lgnetic."
1t is then separated by magnetic
separator, and the zinc-blcrda is thus
recovered.
In nearly all cases of the carbonatcs
of iron similarly treated, minute glob-
ules or metallic iron are contained in
the roasted oxide. Furthermore, the
expulsion Of the carbon dioxide con-
tanned in the ore, with contact of carbon
at certain heat, approXimates to the
conditions of the blast furnace and
favors the reduction of part of tho fer
rous oxide to the metallic state. The
roasted carbonate is always strongly
magnetic. But, from the fusible nature
of the ore, it is extremely difficult to
prevent it from melting during the pro-
cess, SO that nearly all the associated
minerals assume the form of ''clinkers"
with the ore. This circumstance, togeth-
err with the expense of crushing the ore
sufficiently fine, makes the magneti sep
aration of iron oxide from the gangue ore
improbable in such cases. At Pibram,
zinc-blende is sought, and the oxide of
iron is a secondary product.
Hematite is sometimes magnetic, and,
according to Dana, even magneti-po polar
of course, as an incidental occurrence,
other than in crystallizcd specimens.
On account of its rarity, as we'll as the
feebleness of the attraction it presents,
magnetic hematite is not available for
practical purposes. Martitc, the iso-
metic ferric oxide which is supposed to
be a pseudomorph after magnetic, is
attracted by the magnet. The famous