Blue kyanites are aluminum silicate minerals with the chemical formula Al₂SiO₅. Known for their striking blue blade-like crystals, these specimens form under high-pressure metamorphic conditions and are often used to study mineral alignment and metamorphic grade in rocks such as schist and gneiss.
Features:
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Composition: Made of aluminum silicate, kyanite is polymorphic with andalusite and sillimanite, meaning they share the same chemical composition but form under different temperature and pressure conditions.
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Appearance: Typically long and bladed, with color ranging from pale to deep blue. Specimens often exhibit a pearly to vitreous luster and visible crystal striations.
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Formation: Found in high-pressure metamorphic rocks, especially those formed during regional metamorphism of pelitic (clay-rich) sediments.
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Physical Properties: Unusual for having different hardnesses depending on crystal orientation—about 4.5 parallel to the length and 6.5–7 across. This anisotropy makes it useful in studying crystal structure.
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Educational Value: Excellent for teaching about metamorphism, crystal habit, and polymorphism in mineral systems.
Blue kyanites are valued both for their vivid appearance and their role in illustrating complex geologic processes.
