Kyanite Identification Guide
A field guide to recognizing kyanite by its bladed crystals, streaky blue color, and famous directional hardness.
Read the full Kyanite encyclopedia entry →
What Kyanite Looks Like
Kyanite is an aluminosilicate (Al2SiO5) that forms long, flat, bladed crystals. Its color is most often sky-blue to deep sapphire-blue, frequently with darker blue streaks running down the center of the blade and paler, sometimes white or gray, margins. Green, gray, and colorless varieties also exist. The luster is vitreous on crystal faces and distinctly pearly on cleavage surfaces, and crystals range from translucent to transparent.
Crystal habit
- Long, thin, splintery blades, often slightly bent or curved
- Blades commonly grouped in fan-like or radiating aggregates
- Embedded in quartz, mica schist, or gneiss
Step-by-Step Field ID Checklist
- Look for blades. Tabular, knife-like crystals are the strongest first clue.
- Check the color zoning. Patchy blue with darker streaks down the long axis is classic.
- Test hardness in two directions (see below) - this is the defining test.
- Look for the pearly cleavage parallel to the blade.
- Check the host rock - kyanite favors mica schist and quartz veins.
Key Diagnostic Tests
- Anisotropic hardness (diagnostic): Kyanite scratches at about Mohs 4.5-5 along the length of the blade but 6.5-7 across it. A steel knife will scratch the blade lengthwise but skid across it. No other common blue mineral does this.
- Cleavage: Perfect parallel to the blade length, giving smooth pearly faces.
- Streak: White (color is in the mineral, not the powder).
- Specific gravity: Heavy, about 3.5-3.7 - noticeably dense for its size.
- No acid reaction, not magnetic.
Common Look-Alikes and How to Tell Them Apart
- Blue tourmaline (indicolite): Forms striated prismatic (rounded-triangular) crystals, uniform hardness 7, no directional softness.
- Sapphire (blue corundum): Hardness 9 in all directions, barrel-shaped crystals, far harder.
- Sillimanite/fibrolite: Same chemistry but fibrous, not bladed, and uniformly hard (~7).
- Blue aragonite or calcite: Soft (3-4), fizz in acid - kyanite never fizzes.
- Dumortierite: Massive to fibrous, not in clean blades, and harder all around.
Where Kyanite Is Found
Kyanite is a high-pressure metamorphic mineral. Look for it in kyanite-bearing schists and gneisses and in quartz veins cutting them. Major sources include Brazil, Nepal, Switzerland (St. Gotthard), Kenya, India, and the Appalachian belt of the U.S. (notably North Carolina, Georgia, and Virginia).
Frequently asked questions
How can you tell if it's real kyanite?
Test the hardness in two directions. Real kyanite is soft enough (Mohs 4.5-5) to scratch with a knife along the length of the blade but hard (6.5-7) across the blade. Combined with bladed crystals, streaky blue color, and pearly cleavage, this directional hardness is conclusive.
What does kyanite look like?
It forms long, flat, knife-like blue blades, often with darker blue streaks down the middle and paler edges, with a vitreous-to-pearly luster, typically embedded in mica schist or quartz.
Kyanite vs sapphire - how do you tell them apart?
Sapphire is hardness 9 in every direction and forms barrel-shaped crystals, while kyanite is much softer (4.5-5 lengthwise) and forms thin blades. A simple scratch test separates them instantly.
Is kyanite magnetic or does it react to acid?
No. Kyanite is non-magnetic and does not fizz in dilute acid, which helps rule out look-alikes like blue calcite or aragonite that effervesce.
Kyanite identified by the community
Recent Kyanite specimens identified with Rock Identifier.
