Knowra Amphibolite Amphibolite Amphibolite is a metamorphic rock composed mainly of amphibole minerals and plagioclase feldspar. It typically forms when mafic rocks undergo medium- to high-grade metamorphism.
Amphibole : Amphibole is a group of inosilicate minerals characterized by double chains of silica tetrahedra and commonly containing iron, magnesium, calcium, or sodium. Amphibole minerals supply amphibolite’s defining dark, elongate crystals.
Amphibolite facies : Amphibolite facies is a metamorphic facies marked by amphibole- and plagioclase-bearing assemblages at moderate to high temperatures. The rock’s name also describes a facies in which amphibolite commonly forms.
Garnet amphibolite : Garnet amphibolite is amphibolite containing conspicuous garnet alongside its amphibole and plagioclase. Garnet-bearing examples record a distinctive mineral assemblage within the rock type.
Dimension stone : Dimension stone is natural rock quarried and cut to specified sizes for construction or decoration. Dense, durable amphibolite can be quarried and finished as dimension stone.
Plagioclase : Plagioclase is a series of feldspar minerals whose compositions range between sodium-rich albite and calcium-rich anorthite. Plagioclase is the other principal mineral group in typical amphibolite.
Metamorphic reaction : A metamorphic reaction is a mineral-changing chemical reaction driven by changes in pressure, temperature, or fluid composition within a rock. Reactions transform mafic minerals into the amphibole and plagioclase assemblage.
Retrograde metamorphism : Retrograde metamorphism is mineral alteration during cooling or decompression after a rock reaches peak metamorphic conditions. Retrograde minerals can overprint amphibolite formed at higher temperatures.
Aggregate : Aggregate is granular material, including crushed rock, used in concrete, road construction, and other engineering applications. Crushed amphibolite can serve as hard, durable aggregate.
Basalt : Basalt is a fine-grained mafic volcanic rock composed mainly of plagioclase and pyroxene. Basalt can become amphibolite through regional metamorphism.
Regional metamorphism : Regional metamorphism alters rocks over broad areas through elevated pressure and temperature, commonly during mountain building. Large-scale burial and heating commonly metamorphose mafic protoliths into amphibolite.
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