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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.
Pressure oxidation is a process for extracting gold from refractory ore. The most common refractory ores are pyrite and arsenopyrite , which are sulfide ores that trap the gold within them. Refractory ores require pre-treatment before the gold can be adequately extracted. [ 1 ]
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 ...
Mineral alteration refers to the various natural processes that alter a mineral's chemical composition or crystallography. [1]Mineral alteration is essentially governed by the laws of thermodynamics related to energy conservation, relevant to environmental conditions, often in presence of catalysts, the most common and influential being water (H 2 O).
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 ...
The process of formation involves oxidation of Ni 2+ and Fe 2+ which is contained within the primary pentlandite-pyrrhotite-pyrite assemblage. Continued oxidation of polydymite leads to replacement by goethite and formation of a gossaniferous boxwork, with nickel tending to remain as impurities within the goethite or hematite, or rarely as ...