other names: Magnetic iron
mineral class: Oxides and hydroxides
chemical formula: Fe3O4
Chemical elements: Iron, oxygen
Similar minerals: /
shine: Matt, metallic luster
crystal structure: cubic
mass density: 5,1
Mohs hardness: 6
stroke color: black
use: Electrical industry, pigment color
General information about magnetite:
lodestone or magnetite describes a mineral within the spinel group that is assigned to the oxides and occurs as a stable form of the iron-oxygen compound. Magnetite forms crystals that appear as octahedron or rhombic dokaeder, extremely rare as hexahedra, the aggregates are of edge-rounded to dicey form. Gemination is relatively common in magnetites. The mineral is completely opaque and has a striking metallic luster, but may occasionally show a dull surface. It is of mussel breakage and perfect cleavage. The color of magnetite appears iron-black, on crystal surfaces often shows a bluish color, which arises by tarnishing. To prove the authenticity of magnetite, simply testing its strong magnetism is needed. The mineral melts only at temperatures of well over 1500 ° C and shows when heated to about 580 ° C a red annealing color. If the magnetite is subsequently brought to cool quickly, it temporarily loses its magnetism. Only after complete cooling does he regain his magnetic properties.
Origin, occurrence and localities:
Magnetite can only develop at temperatures of over 600 ° C and arises in the course of the so-called contact pneumatolysis, that is, as a result of overmoulding of rocks by magmatic gases. The rocks from which magnetite can develop must be lime, silicate or sulfide. As a mixture part magnetite can be detected in almost all Magmagesteinen. Thus, magnetite crystals are often found in basalt at the bottom of the oceans. Occasionally magnetite is also contained in sediments, which is due to its high weathering stability.
The magnetic mineral is widespread all over the world and is mined on a large scale, especially in Greenland, the British Isles, Scandinavia, in large parts of Central and Southern Europe and North, Central and South America. Turkey, many African countries, Russia and the Ukraine, Mongolia, China, Japan and India as well as Australia and New Zealand have economically significant deposits.
History and usage:
The use of magnetite due to its magnetic properties dates back to the eleventh century BC and began in ancient China. The present name of the mineral developed only in the 19th century from the old name Magnetic Ironstone, which was in use from the Middle Ages.
Magnetite plays an important role as a raw material in the electrical industry because of its strong magnetism. In addition to hematite, with an iron content of over seventy percent, it is considered one of the most important iron ores in the industry and is indispensable for ore extraction. In powdered form, magnetite is used as a dark pigment in paints, coatings and various colors. The mineral plays an important role in science, as it is detectable in the organism of many animals, especially flying insects and birds, where it serves as a guide in the earth's magnetic field. Scientists are also intensively researching the importance of magnetite located at the ocean floor for the continental and pole shift in the course of Earth's history.