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Magnetite crystals with a cubic habit are rare but have been found at Balmat, St. Lawrence County, New York, [47] [48] and at Långban, Sweden. [49] This habit may be a result of crystallization in the presence of cations such as zinc. [50] Magnetite can also be found in fossils due to biomineralization and are referred to as magnetofossils. [51]
Michel-Lévy interference colour chart issued by Zeiss Microscopy. In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope.
Vacancies lower the crystal symmetry. Therefore, monoclinic forms of pyrrhotite are in general more defect-rich than the more symmetrical hexagonal forms, and thus are more magnetic. [11] Monoclinic pyrrhotite undergoes a magnetic transition known as the Besnus transition at 30 K that leads to a loss of magnetic remanence. [12]
A and B can also be the same metal with different valences, as is the case with magnetite, Fe 3 O 4 (as Fe 2+ Fe 3+ 2 O 2− 4), which is the most abundant member of the spinel group. [3] Spinels are grouped in series by the B cation. The group is named for spinel (MgAl 2 O 4), which was once known as "spinel ruby". [4] (Today the term ruby is ...
Under reflected light, magnetite shows up as metallic and a silver or black color. Hematite will be a more reddish-yellow color. Pyrite is seen as opaque, a yellow-gold color, and metallic. [12] Chamosite is an olive-green color in thin section that readily oxidizes to limonite. When it is partially or fully oxidized to limonite, the green ...
Hausmannite is a complex oxide, or a mixed oxide, of manganese containing both di-and tri-valent manganese. Its chemical formula can be represented as Mn II Mn III 2 O 4, or more simply noted as MnO·Mn 2 O 3, or Mn 3 O 4, as commonly done for magnetite (Fe 3 O 4), the corresponding iron oxide.
The magnetic moment and the magnetic field of the electromagnet are proportional to the number of loops of wire, to the cross-section of each loop, and to the current passing through the wire. [45] If the coil of wire is wrapped around a material with no special magnetic properties (e.g., cardboard), it will tend to generate a very weak field.
The streak of limonite on an unglazed porcelain plate is always yellowish brown, a character which distinguishes it from hematite with a red streak, or from magnetite with a black streak. The hardness is quite variable, ranging from 1 to 5. In thin section it appears as red, yellow, or brown and has a high index of refraction, 2.0–2.4.