An octahedron
of Magnetite in a chlorite schist.
Octahedral Magnetite crystals from Cerro
Huanaquino Potosi, Bolivia.
Modified Cube
A massive piece of Magnetite showing a magnetic attraction to paper clips.
Magnetite is always magnetic in that it is attracted to a magnet.
Magnetite can also be a natural magnet in a variety known as Loadstone.
Magnetite (stretched
octahedrons) replaced by Hematite. aka Hematite psuedomorph after
magnetite.
CHEMISTRY Fe3O4
CRYSTALLOGRAPHY Isometric (Cubic)
CRYSTAL GROWTH AND HABITS Magnetite crystals are commonly octahedral and occasionally dodecahedral and rarely cubic. It can also be granular to massive.
COLOR AND OTHER OPTICAL PROPERTIES Magnetite is black to gray with a slight brownish hue.
HARDNESS 5.5-6.5
SPECIFIC GRAVITY 5.2
LUSTER Metallic to submetallic and dull
STREAK Black
BREAKABILITY Uneven fracture, brittle
OCCURRENCE A common accessory mineral in igneous and metamorphic rocks. It is also found in sedimentary layers as banded iron ore formations.
ASSOCIATED MINERALS Chromite, Ilmenite, Rutile, Pyrite, Hematite
OTHER PROPERTIES Strongly magnetic