Knowra Epidote Epidote Epidote is a calcium–aluminium–iron sorosilicate mineral, typically green, found in metamorphic rocks and hydrothermal veins. Its composition varies chiefly with iron substituting for aluminium.
Sorosilicate : A silicate mineral whose structure contains pairs of linked silica tetrahedra. Epidote belongs to this structural class, built around paired silicon–oxygen groups.
Isomorphous substitution : Replacement of one chemical element by another within a mineral structure without changing its basic structure. Iron substitutes for aluminium in epidote, creating compositional variation within the species.
Metamorphic petrology : The study of mineral assemblages, reactions, and conditions in metamorphic rocks. Epidote’s presence and composition help identify metamorphic reactions and conditions.
Actinolite : A green to gray-green amphibole mineral rich in calcium, magnesium, and iron. Its elongated crystals and cleavage can resemble epidote, but its amphibole structure differs.
Epidote group : A mineral group of structurally related sorosilicates with varied compositions. Epidote is the group’s namesake species, alongside minerals with substitutions in key chemical sites.
Metamorphic reaction : A chemical change among minerals as rocks respond to new pressure, temperature, or fluid conditions. Epidote forms in reactions that reorganize calcium, aluminium, iron, and silica in metamorphosed rocks.
P–T–t path : A reconstruction of a rock’s pressure, temperature, and time history. Changes in epidote-bearing assemblages can constrain stages of a rock’s metamorphic history.
Chlorite group : A group of sheet silicate minerals commonly found in low-grade metamorphic rocks. Chlorite often shares epidote’s green settings, but its platy habit and sheet structure distinguish it.
Clinozoisite : A monoclinic epidote-group mineral with little or no iron replacing aluminium. Comparing it with epidote shows how iron content changes composition and commonly affects color.
Hydrothermal alteration : Chemical and mineralogical change in rocks caused by circulating hot aqueous fluids. Fluids can introduce or redistribute components that precipitate epidote in veins and altered rocks.
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