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The formation of goethite is marked by the oxidation state change of Fe 2+ (ferrous) to Fe 3+ (ferric), which allows for goethite to exist at surface conditions. Because of this oxidation state change, goethite is commonly seen as a pseudomorph. As iron-bearing minerals are brought to the zone of oxidation within the soil, the iron turns from ...
Pyrite (FeS 2) has oxidised to form goethite (FeO(OH)) and limonite (FeO(OH)·nH 2 O), [2] which form a porous covering over the oxidized zone known as a gossan cap or iron hat. [4] Prospectors use gossan as an indication of ore reserves.
Violarite (Fe 2+ Ni 2 3+ S 4) is a supergene sulfide mineral associated with the weathering and oxidation of primary pentlandite nickel sulfide ore minerals.. Violarite crystallises in the isometric system, with a hardness of 4.5 to 5.5 and a specific gravity of about 4, is dark violet grey to copper-red, often with verdigris and patina from associated copper and arsenic sulfides, and is ...
Pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion. [47] The solution is the use of buffer blasting and the use of various sealing or cladding agents to hermetically seal the mined-out areas to exclude oxygen.
A pyrite cube has dissolved away from host rock, leaving gold particles behind. Oxidized pyrite cubes. Within the weathering environment, chemical oxidation of a variety of metals occurs. The most commonly observed is the oxidation of Fe 2+ by oxygen and water to form Fe 3+ oxides and hydroxides such as goethite, limonite, and hematite. This ...
These soils contain iron sulfide minerals (predominantly as the mineral pyrite) and/or their oxidation products. In an undisturbed state below the water table, acid sulfate soils are benign. However, if the soils are drained, excavated or otherwise exposed to air, the sulfides react with oxygen to form sulfuric acid. [1]
It is translucent to opaque with a vitreous to dull luster, and is colored dark yellow to yellowish-brown. It can sometimes be confused with limonite or goethite with which it commonly occurs in the gossan (oxidized cap over an ore body). Jarosite is an iron analogue of the potassium aluminium sulfate, alunite.
Silica pseudomorph after gypsum crystals and silicified serpulid polychaete tubes Pseudomorph of goethite after pyrite. In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another due to alteration, or ...