mineral
Black Kyanite
Aluminum Silicate (Al2SiO5)
Hardness: 4.5 along crystal length, 6.5-7 across width; Color: Black to dark gray; Lustre: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in one direction
- Hardness
- 4
- Color
- Black to dark gray
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Physical properties
Hardness: 4.5 along crystal length, 6.5-7 across width; Color: Black to dark gray; Lustre: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in one direction
Formation & geological history
Formed during high-pressure regional metamorphism of clay-rich sedimentary rocks, typically appearing in schists and gneisses. The black color is often due to inclusions of graphite.
Uses & applications
Metaphysical collecting, industrial use in high-heat porcelain and refractory materials, and occasionally used in jewelry.
Geological facts
Kyanite is unique because it has two different hardness ratings depending on the axis it is scratched. The fan-like or blade-like habit of black kyanite is often referred to as 'witches' brooms'.
Field identification & locations
Identified by its bladed, fan-like habit, splintery texture, and graphite-like coloration. Commonly found in Brazil, USA (appalachians), and India.
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