Concentration of Iron Ores. No. 3. [Volume: 8, Issue: 3, 1889, pp. 188-195]

No. 3.]

CHARCOAL IRON WORKERS.

193

most economical purposes may be readily made, the physical
structure of other ores prevents attaining a separation approaching perfections. In one New York State magnetite a microscopic examination which Mr. E. K. Landis made of the ore
after it passed the crushers, rolls and screens showed that however fine the grain, it, in many cases, consisted of molecules of
Fe3 04, SiO2, FeS, and hornblende, pieces about one one-hundredth
of an inch showing under the microscope, magnetite, pyrite,
quartz and sometimes hornblende.
Dr. Eugene Hussak in his monograph on " The determination
of rock forming minerals," says if several ferriferous minerals
occur in the rock to be examined, i. e., magnetite, ilmenite,
augite, biotite, olivine, etc., they can be separated from each
other by varying the strength of the current passing through the
electro-magnet. At first two elements are used, then four, six,
eight and finally ten. Doelter has shown that the minerals can be
arranged in a series according to their power of being attracted.
He gives thirty-three minerals and indicates their order in the
power of being attracted by magnets.
Dana says magnetite is strongly magnetic, and sometimes
possess polarity, and that from the normal proportions of one
part of Fe O to one of Fe2 03 there is occasionally a wide variation,
and thus a gradual passing to the sesquioxide [Fe2 03]; he instances analyses from Bengal, india, in which the proportion of Fe2
03 to FeO was nearly three to one, in an ore which was strongly
magnetic and columnar, while another ore from the same locality in which the proportion of Fe2 03 to FeO was in the proportion of three and a quarter to one was granular, and not polar
magnetic. He also says that hematite is sometimes attracted
by a magnet, and occasionally even magneti-polar. Martite
which is supposed to be a psuedomorph, mostly after magnetite
is reported as non-magnetic or only feebly so. Menacanite
slightly influences the magnetic needle.
The presence of certain of these minerals will materially
affect the results obtained, as we naturally look for a better
separation when the material in the gangue is but slightly attracted by the magnet or practically insensible to its influence.
In the Transactions of the American Institute of Mining En5