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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 ...
Moqui Marbles, hematite, goethite concretions, from the Navajo Sandstone of southeast Utah. The "W" cube at the top is one cubic centimeter in size. Moqui Marbles , also called Moqui balls or "Moki marbles", are iron oxide concretions which can be found eroding in great abundance out of outcrops of the Navajo Sandstone within south-central and ...
Martian spherules (also known as hematite spherules, blueberries, & Martian blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey hematite, α-Fe 2 O 3) and are found at Meridiani Planum (a large plain on Mars) in exceedingly large numbers.
It was also argued that the hematite nodules represent pyrite concretions oxidized by weathering of near surface pyrophyllite deposits. Below the near-surface zone of weathering, which has developed in the pyrophyllite, pyrite concretions are unaffected by weathering and, thus, have not been altered to hematite.
In geology and particularly in sedimentology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition from the enclosing sediment or sedimentary rock. Examples include pyrite nodules in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale.
The dominant minerals in the oxide facies are magnetite and hematite. The dominant minerals in the silicate facies are greenalite, minnesotaite, and glauconite. The dominant mineral in the carbonate facies is siderite. The dominant mineral in the sulfide facies is pyrite. Most iron formations are deformed or metamorphosed simply due to their ...
The term "polymetallic ore" also includes nodules, principally Manganese nodules, that do not form as terrestrial deposits but as concretions on the ocean floor. [3] [4] Rocks containing polymetallic ores are often altered or formed by hydrothermal processes — chloritization, sericitization and silicification.
Extensive successions of laminated or massive mudstone are common, often containing slickensides, calcareous nodules or layers , and/or hematite nodules. These types of thick mud/marl layers likely formed in more quiet parts of the floodplain isolated from turbulent channels. [1]