Identification guide · Minerals
How to Identify Kyanite
Kyanite is usually blue, green, and orange with a vitreous luster and is translucent. It has a Mohs hardness of 5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is white. It is most often confused with Corundum, Diopside, and Labradorite; the tests below separate them.
Kyanite identification checklist
| Color | Blue, Green, Orange, Black | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 5 | A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect | |
| Fracture | Fibrous | |
| Specific gravity | 3.6 | Heavier than it looks (specific gravity about 3.6). |
| Crystal system | Triclinic |
Kyanite look-alikes and how to tell them apart
Corundum is harder (Mohs 9) than Kyanite (Mohs 5), so Corundum will scratch Kyanite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Kyanite vs Corundum →
Diopside is harder (Mohs 5.5–6.5) than Kyanite (Mohs 5), so Diopside will scratch Kyanite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Kyanite vs Diopside →
Labradorite is harder (Mohs 6) than Kyanite (Mohs 5), so Labradorite will scratch Kyanite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Kyanite vs Labradorite →
Both sit near Mohs 5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Check whether the specimen's color and texture match typical Kyanite examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Kyanite identification FAQ
How can you tell if a rock is Kyanite?
Check the color (blue, green, orange, and black), the vitreous luster, a Mohs hardness of 5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Kyanite?
Kyanite has a Mohs hardness of 5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Kyanite and Corundum?
Kyanite (Mohs 5, vitreous luster) and Corundum (Mohs 9, adamantine to vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Kyanite vs Corundum comparison for a side-by-side table.
Is Kyanite worth anything?
Entry-level Kyanite specimens sell for around $10, typical collector pieces about $50, and premium examples $300 or more depending on size, quality and locality.
What color is Kyanite?
Kyanite is most often blue, green, orange, and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
