Knowra Staurolite Staurolite Staurolite is a brown to black iron-aluminium silicate mineral found chiefly in metamorphic rocks. Its crystals commonly form distinctive cross-shaped twins.
Silicate minerals : Minerals built from silicon–oxygen tetrahedra, alone or combined with other elements. Staurolite belongs to this broad mineral group, whose structures shape its composition.
Metamorphic facies : Assemblages of metamorphic minerals that indicate characteristic pressure and temperature conditions. Staurolite marks particular metamorphic conditions when considered with its associated minerals.
Metamorphic petrology : The study of rocks transformed by heat, pressure, and chemically active fluids. Petrologists use staurolite-bearing assemblages to interpret metamorphic histories.
Fairy stones : Naturally twinned staurolite crystals, especially cross-shaped specimens collected in parts of the southeastern United States. These specimens are the familiar cross-shaped expression of staurolite twinning.
Staurolite crystal structure : The arrangement of atoms in staurolite’s crystal lattice, commonly described using a monoclinic unit cell. Its lattice accounts for the mineral’s characteristic crystal forms and twinning.
Barrovian metamorphism : Regional metamorphism in which mineral zones commonly develop with increasing metamorphic grade. Staurolite commonly appears in the intermediate-grade zones of this regional sequence.
Metamorphic index mineral : A mineral whose stability range helps indicate the grade or conditions of metamorphism. Staurolite can identify intermediate metamorphic grades in suitable rocks.
Staurolite Falls : A locality in Georgia, USA, associated with naturally occurring cross-shaped staurolite crystals. Its crystals illustrate the mineral’s regional occurrence and distinctive twin forms.
Metamorphic rock : Rock transformed from pre-existing rock by heat, pressure, or chemically active fluids. Staurolite typically crystallizes during metamorphism rather than in ordinary igneous settings.
Porphyroblast : A large metamorphic crystal that grew within a finer-grained rock matrix. Staurolite often grows as conspicuous porphyroblasts in schist.
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