Knowra Kyanite Kyanite Kyanite is an aluminosilicate mineral, typically blue, whose hardness varies markedly with direction in its crystal. It is a high-pressure indicator mineral in metamorphic rocks.
Aluminosilicate : A mineral or material composed primarily of aluminum, silicon, and oxygen. Kyanite is one crystalline arrangement of aluminum silicate.
Mineral hardness : A mineral’s resistance to scratching, commonly measured by comparison with reference minerals. Kyanite is unusually soft when scratched parallel to one crystal direction and harder across it.
Metamorphic petrology : The study of rocks transformed by heat, pressure, and chemically active fluids. Petrologists use kyanite-bearing rocks to interpret metamorphic conditions.
Andalusite : An Al2SiO5 mineral stable at lower pressures than kyanite under many metamorphic conditions. It has the same composition as kyanite but a distinct structure and stability field.
Crystal structure : The ordered, repeating arrangement of atoms in a crystalline solid. Kyanite’s arrangement of aluminum, silicon, and oxygen helps produce its directional properties.
Crystal habit : The characteristic external shape in which a mineral crystal grows. Kyanite’s elongated, bladed crystals reflect its growth and internal structure.
Index mineral : A mineral whose presence helps indicate the conditions under which a metamorphic rock formed. Kyanite indicates relatively high pressure within appropriate rock compositions.
Sillimanite : An Al2SiO5 mineral commonly stable at higher temperatures than kyanite. Its stability contrasts with kyanite’s, helping distinguish metamorphic histories.
Anisotropy : The variation of a material’s properties with direction. Kyanite’s hardness changes with direction because its properties are anisotropic.
Metamorphic facies : A set of mineral assemblages characteristic of particular pressure and temperature conditions. Kyanite belongs to assemblages that record relatively high-pressure metamorphism.
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