|
|
|
What is Magnetite
Magnetite is a natural magnet, hence the name, giving it a very nice distinguishing characteristic. Explaining the magnetism is not easy but here is a go at it. Remember, electricity produces magnetic fields just as magnetism produces electic fields. Magnetite is a member of the spinel group which has the standard formula A(B)2O4. The A and B represent usually different metal ions that occupy specific sites in the crystal structure. In the case of magnetite, Fe3O4, the A metal is Fe +2 and the B metal is Fe +3; two different metal ions in two specific sites. This arrangement causes a transfer of electrons between the different irons in a structured path or vector. This electric vector generates the magnetic field.
PHYSICAL CHARACTERISTICS:
-
Color is black.
-
Luster is metallic to dull.
-
Transparency: Crystals are opaque.
-
Crystal System is isometric; 4/m bar 3 2/m
-
Crystal Habits are typically octahedrons but rarely rhombododecahedron and other isometric forms, most commonly found massive or granular. Twinning of octahedrons into spinel law twins is seen occassionally.
-
Cleavage is absent although octahedral parting can be seen on some specimens.
-
Fracture is conchoidal.
-
Hardness is 5.5 - 6.5
-
Specific Gravity is 5.1+ (average for metallic minerals)
-
Streak is black.
-
Associated Minerals are talc and chlorite (schists), pyrite and hematite.
-
Other Characteristics: Magnetism stronger in massive examples than in crystals, striations on crystal faces (not always seen).
-
Notable Occurrences include South Africa, Germany, Russia and many locallities in the USA.
Best Field Indicators are magnetism, crystal habit and streak.
|
|
