Kyanite
Kyanite (formerly Disthene) · Collector Mineral / Semi-Precious Gemstone
Crystal System
Triclinic; commonly occurs in long, bladed crystals, frequently aggregated and often bent or distorted.
Mineral Group
Silicates (Nesosilicate); Andalusite group polymorph
Chemical Formula
Al2SiO5 (Aluminum Silicate)
Formation Process
Metamorphic; forms under high-pressure regional metamorphism of clay-rich sediments. It is a key index mineral for determining metamorphic facies.
About This Crystal
The specimen shows characteristic bladed crystal habits with a sub-vitreous to pearly luster. It exhibits a range of colors including sky blue, grey-blue, and orange-tinted weathering, with translucent to opaque transparency.
Physical Characteristics
Color: Blue, grey, white, or orange; Streak: White; Cleavage: Perfect in one direction {100}, good in another {010}; Fracture: splintery; Specific Gravity: 3.53–3.67; Tenacity: Brittle; Fluorescence: Weak red under UV.
Optical Properties
Refractive Index: 1.712–1.734; Birefringence: 0.015-0.020; Pleochroism: Strong (colorless to light blue to dark blue); Optically Biaxial negative.
Hardness & Durability
Origin Region
Notably sourced from Brazil, Nepal, Russia (Urals), Switzerland, and the USA (North Carolina). Typically found in aluminum-rich metamorphic rocks like Schist and Gneiss.
Hardness & Durability
Highly anisotropic hardness: 4.5 to 5.0 parallel to the long axis and 6.5 to 7.0 across the crystals. Poor toughness due to perfect cleavage; low wearability in rings.
Care & Maintenance
Clean with warm soapy water only; avoid ultrasonic and steam cleaners. Store separately from harder gemstones like sapphire to prevent scratching. Susceptible to fracturing along cleavage planes if dropped.
Rarity & Value
Common globally as a mineral, but gem-quality transparent material is uncommon. Value is driven by color intensity (deep sapphire blue is preferred) and clarity. Heat treatment is not common.
Special Characteristics
Anisometric hardness (variable hardness based on direction) is its most distinctive feature. Occasionally shows chatoyancy when cut as cabochons.
Lore & History
Historically used as a compass by travelers who believed it could follow Earth's magnetic force when suspended by a hair. In modern crystal healing, it is traditionally associated with the Throat Chakra and thought to promote communication and self-expression.