Maghaemite
Ferrimagnetic mineral. Utilised in certain magnetic recording tapes. Alteration product (fully oxidised from of magnetite), present in certain soils. Chemical formula γ-Fe2O3. Maghaemite is metastable, when heated and transforms into haematite.

Magnetic anisotropy
Variation of magnetic properties with direction.

Magnetic dipole
Ensemble of two equal magnetic charges of opposite sign.

Magnetic domains
Regions in a solid, where the magnetic moments of the atoms are parallel; separated by walls. They form spontaneously to minimise the potential energy of a magnetised material. For certain grain or crystal sizes, an entire grain may magnetised in the same direction (single domain behaviour). Equidimensional grains of magnetite are single domain between grain sizes of 0.025 to 0.060 micrometres (10-6 m). The single domain range for equidimensional  haematite is much larger, it ranges from 0.025-0.030 up to 15  micrometres.

Magnetic field
Force field in the vicinity of a magnet or electrical current. Also magnetic induction or magnetic flux density. Unit is A/m. The unit of the Earth magnetic field is the unit of induction or Tesla.

Magnetic hysteresis
The magnetisation induced in a sample by a magnetic field lags behind the field. After removal of the field the sample possesses a remanent magnetisation.

Magnetic meridial plane
Local vertical plane containing magnetic north.

Magnetic minerals

rockmagnetic properties
Mineral
 Chemical formula
 Magnetic low field susceptibility
 Tn, Tc
                          
Saturation magnetisation @ room temperature
 Saturation magnetisation @ room temperature


10-8 m3/kg (*)
 °C
 kA/m
 Am2/kg
magnetite
 Fe3O4
 578
 580 - 585
 480
 92
maghaemite
 γ-Fe2O3
 500
 ~620
590 - 675
 380
 85
haematite
 α-Fe2O3
 25
 675
 ~2.5
 0.5
goethite
 α-FeOOH
 0.5 - 1.5
 120
 ~2
 ~1
(*) these values are indicative, the magnetic susceptibility depends strongly on grain size

crystallographic properties
Mineral
 Chemical formula
 Crystallographic system
 Unit cell diameter
                          
Density
 Transformation temperature



A
 kg/m3 °C
magnetite
 Fe3O4
 cubic inverse spinel
 8.396
 5.197
maghaemite
 γ-Fe2O3
 cubic or tetragonal spinel
 8.337 (a)
24.99 (c)
 5.074
 250 - 750
haematite
 α-Fe2O3
 rhombohedric
 5.034 (a)
1.375 (c) 		5.271
goethite
 α-FeOOH
 orthorhombic
 4.596 (a)
9.956 (b)
3.021 (c)
 4.264
 250 - 400


Magnetic moment
Expresses the magnetic intensity of a magnet. A couple of forces acting on a magnet put perpendicular to a uniform magnetic field with a magnetic flux density equal to the unit. The unit of the magnetic moment is Am2.

Magnetic multipole
Ensemble of even-numbered equal magnetic charges of opposite sign. A quadrupole is an ensemble of two north and two south poles. About 5% of the interior geomagnetic field are caused by a field of multipoles.

Magnetic north/south pole
Point on the surface of the Earth, where the observed magnetic inclination is +90° (magnetic north pole) or -90° (magnetic south pole) and where the horizontal component of the geomagnetic field is zero. The magnetic poles are currently situated at:

North magnetic pole (in 2001): 81.3° N and 110.8° W, near Elef Ringes island (Canada)
South magnetic pole (in 2001): 64.7° S and 138.0° E in the bay Commonwealth Bay (Antarctica)

Magnetic susceptibility
Measure of the ability of a sample to acquire a magnetisation in a magnetic field (magnetisability). Ratio of the magnetisation M induced in the sample over the inducing magnetic field H. k= M/H.

Magnetisation (M)
Magnetic moment per unit of volume (A/m) or per unit of weight (Am2/kg) of a magnetised sample. In the presence of magnetic field one speaks about an induced magnetisation being the sum of two components: remanent magnetisation (magnetisation that remains when the magnetic field is removed) and transient magnetisation (magnetisation that disappears when the magnetic field is removed), otherwise it is called remanent magnetisation. AD


Magnetite
Ferrimagnetic mineral. Very common in the majority of volcanic, metamorphic and sedimentary rocks. Is also produced by certain bacteria: intracellular by magnetotactic bacteria and extracellular by iron reducing bacteria. Named after Magnès, who after Plinius the old discovered stones that attracted iron. According to another version the denomination magnetite should come from the locality of Magnesia in Macedonia where it was discovered. Magnetite forms granular to compact masses, more rarely it crystallises into tetrahedrons and dodecahedrons. The colour is black with blue metallic reflectance. In powder form the colour is black. Strongly magnetic mineral. Iron ore. Hardness from 5.5 to 6.

Merovingian
Denotes a time when the Merovingian dynasty (dynasty of Frankish kings) who ruled territories in the present day Germany and France from the 5th to the 8th century AD.

Minoan period
Cultural period in Greece between 2000 and 1400 BC, subsequent to the Early Bronze age (2900-2000 BC) and followed by the Mycenaean age. The Greek Bronze-age civilisation was centred in Crete and the surrounding islands. The terrible eruption of the Santorini volcano around 1600 BC may be to certain extend responsible for the disappearance of the Minoan civilisation in Crete.

Mycenaean age
Cultural period in Greece between 1100 and 600 BC, subsequent to the Minoan period and followed by the Dark ages. This period was characterised by high cultural achievement, being the basis of myths and heroes later on.