Kyanite
Kyanite is one of mineralogy's most fascinating anomalies — its hardness varies dramatically depending on direction. Running a knife along the blade scratches easily (H 4.5); running it across is much harder (H 6.5–7). This directional hardness (anisotropy) is unique and diagnostic. Blue kyanite blades from North Carolina are popular collector specimens and can be faceted into striking blue gems.
Physical Properties
Chemical Formula
Al₂SiO₅
Hardness (Mohs)
4.5–5 (along length) / 6.5–7 (across)
Color
Blue, green, orange, colorless — often blue-white blades
Luster
Vitreous to pearly
Crystal System
Triclinic
Streak
White
Cleavage
Perfect in one direction, good in second
Specific Gravity
3.53–3.67
🔍 Field Identification Tips
Long bladed crystals (blade-like habit) in blue or blue-white is distinctive. Test hardness in two directions — if it varies dramatically, it's kyanite. Perfect cleavage along the blade length. Often found with garnet, staurolite, and biotite in metamorphic rocks. Distinguished from sapphire by habit (blades vs. hexagonal crystals) and variable hardness.
Varieties & Forms
📍 Where to Find Kyanite in the US
Uses & Applications
Refractory ceramics, spark plugs, porcelain insulators, jewelry (faceted gems and cabochons).
💰 Collector Value Guide
Common rough: $5–$30/lb. Gem-quality North Carolina blue: $20–$200/specimen. Faceted kyanite: $10–$100/ct. Fine translucent blue: $100–$500/ct.
Find Kyanite With Our Tools
Use the We Lick Rocks app to identify specimens, find dig sites, and connect with local rockhounds.