Iron oxide (Fe3O4)
Color: Brownish to black
Luster: Metallic to semi-metallic,
splendant to dull
Specific Gravity: 5.18
Habit: Crystals are octahedral and
dodecahedral. Aggregates are massive,
compact, and fine to coarse granular.
Magnetite is a heavy black mineral that
is easily identified because it is
strongly attracted by a magnet. A few
other minerals are weakly attracted by
magnets, but they either do not look
like magnetite or their streaks are not
black. Magnetite from some localities
acts as a natural magnet (that is, will
attract iron filings), and is called
lodestone. Magnetite is a relatively
abundant mineral, for it is a minor constituent of many different types of
rocks. Where it is sparser disseminated as large grains in some rocks,
the characteristic octahedral crystal
form of magnetite is often identifiable.
However, the grains are most commonly
irregular in shape. Being an oxide,
magnetite is highly resistant to
alteration by weathering, so grains of
it tend to accumulate in sands. As a
result, the easiest way to find
magnetite is to thrust a magnet into the
sand of almost any stream or beach.
Magnetite is a very important mineral to
our industrial economy, for it is one of
the principal ore minerals of iron.
in Which this Mineral is Found
Specimen Description: Magnetite, right
crystal 2.3 cm high, San Gabriel
Mountains, Los Angeles County.
California State Mining and Mineral
Photographer: Jeff Scovil