RocksdayAmethyst vs Sugilite
How to tell them apart
The purple variety of quartz. Its color comes from traces of iron combined with natural radiation, and it often lines the inside of large volcanic geodes.
Photo: Gonzalo Devia, CC BY-SA 4.0
A rare, intensely magenta-purple silicate prized for cabochons.
Photo: RDCnet, CC BY-SA 4.0
Key differences
- Amethyst is transparent quartz.
Side by side
| Property | Amethyst | Sugilite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7 | 5.5–6.5 |
| Luster | Vitreous | Vitreous to waxy |
| Streak | White | White |
| Colors | Purple | Purple, Pink |
| Crystal system | Trigonal | Hexagonal |
| Specific gravity | 2.65 | 2.74–2.8 |
| Formula | SiO₂ | KNa₂(Fe,Mn,Al)₂Li₃Si₁₂O₃₀ |
| Found in | Rio Grande do Sul, Brazil; Artigas, Uruguay | Wessels mine, South Africa; Iwagi Island, Japan |
Properties that are the same for both are grayed out.
How to identify amethyst
- Purple, often deepest at the crystal tips.
- Hardness 7 — scratches glass.
- Grows as clusters of pointed crystals inside geodes.
- No cleavage; breaks with a glassy, curved fracture.
Crystal system: Trigonal
Full Amethyst guide →How to identify sugilite
- Deep magenta to grape purple, usually opaque.
- Often mottled with black manganese minerals.
- Hardness about 6.
Crystal system: Hexagonal
Full Sugilite guide →More comparisons
Could you tell them apart from a blurry close-up?
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