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Hematite (/ ˈ h iː m ə ˌ t aɪ t, ˈ h ɛ m ə-/), also spelled as haematite, is a common iron oxide compound with the formula, Fe 2 O 3 and is widely found in rocks and soils. [6] Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe 2 O 3. It has the same crystal structure as corundum ...
Metallic iron is virtually unknown on the Earth's surface except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths.Although iron is the fourth-most abundant element in the Earth's crust, composing about 5%, the vast majority is bound in silicate or, more rarely, carbonate minerals, and smelting pure iron from these minerals would require a prohibitive amount of ...
Where present, rare-earth metals tend to associate with phosphate minerals. When iron oxide species trend towards magnetite or crystalline massive hematite, IOCG deposits may be economic based on their iron oxide contents alone. Several examples of IOCG deposits (Wilcherry Hill, Cairn Hill, Kiruna) are iron ore deposits.
Iron ore (banded iron formation) Manganese ore – psilomelane (size: 6.7 × 5.8 × 5.1 cm) Lead ore – galena and anglesite (size: 4.8 × 4.0 × 3.0 cm). Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process.
Magnetite reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control how oxidizing its environment is (the oxygen fugacity). This buffer is known as the hematite-magnetite or HM buffer. At lower oxygen levels, magnetite can form a buffer with quartz and fayalite known as the QFM buffer.
Other minerals that form concretions include iron oxides or hydroxides (such as goethite and hematite), [19] [20] dolomite, siderite, [21] ankerite, [22] marcasite, [23] barite, [24] [25] and gypsum. [26] Although concretions often consist of a single dominant mineral, [27] other minerals can be present depending on the environmental conditions ...
A mineral grain from a meteorite preserved evidence that water was present on Mars 4.45 billion years ago, and it may have created hot springs habitable for life.
The Earth's magnetic field at 0.5 gauss is too weak to magnetize a lodestone by itself. [9] [10] The leading theory is that lodestones are magnetized by the strong magnetic fields surrounding lightning bolts. [9] [10] [11] This is supported by the observation that they are mostly found near the surface of the Earth, rather than buried at great ...