RocksdayKyanite vs Sapphire
How to tell them apart
A blue, bladed metamorphic mineral famous for having different hardness in different directions.
Photo: User:Aelwyn, CC BY-SA 3.0
Gem corundum of any color except red. Blue sapphire gets its color from iron and titanium.
Photo: James St. John, CC BY 2.0
Quick tests
- Hardness: Sapphire is clearly harder: Mohs 9 versus 4.5–7.
Key differences
- Kyanite forms blades and is scratched by a knife along its length.
Side by side
| Property | Kyanite | Sapphire |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 4.5–7 | 9 |
| Luster | Vitreous to pearly | Adamantine to vitreous |
| Streak | White | White |
| Colors | Blue, Gray, Green | Blue, Yellow, Pink, Orange |
| Crystal system | Triclinic | Trigonal |
| Specific gravity | 3.53–3.67 | 3.95–4.03 |
| Formula | Al₂SiO₅ | Al₂O₃ |
| Found in | Minas Gerais, Brazil; Nepal | Sri Lanka; Madagascar |
Properties that are the same for both are grayed out.
How to identify kyanite
- Long, flat, blue blades with streaky color.
- A knife scratches it along the length but not across.
- Splits along the blades.
- Found in schist and gneiss.
Crystal system: Triclinic
Full Kyanite guide →How to identify sapphire
- Hardness 9 — only diamond scratches it.
- Barrel or tapered six-sided crystals.
- Heavy for its size.
Crystal system: Trigonal
Full Sapphire guide →More comparisons
Could you tell them apart from a blurry close-up?
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