RocksdayAmethyst vs Grape Agate
To tell Amethyst from Grape Agate: Amethyst grows as pointed crystals, not spheres.
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
Clusters of tiny purple quartz spheres from West Sulawesi that look like a bunch of grapes.
Photo: JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0
Key differences
- Amethyst grows as pointed crystals, not spheres.
Side by side
| Property | Amethyst | Grape Agate |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7 | 6.5–7 |
| Luster | Vitreous | Waxy to vitreous |
| Streak | White | White |
| Colors | Purple | Purple, Green, Blue |
| Crystal system | Trigonal | Botryoidal quartz |
| Specific gravity | 2.65 | 2.6–2.65 |
| Formula | SiO₂ | SiO₂ |
| Found in | Rio Grande do Sul, Brazil; Artigas, Uruguay | West Sulawesi, Indonesia |
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 grape agate
- Round purple (sometimes green or blue) balls packed together.
- Each ball is smooth quartz, not a pointed crystal.
- Scratches glass.
Crystal system: Botryoidal quartz
Full Grape Agate guide →More comparisons
Frequently asked questions
What is the difference between amethyst and grape agate?
Amethyst is a mineral (SiO₂) with a Mohs hardness of 7 and a vitreous luster, usually purple. Grape Agate is a mineral (SiO₂) with a Mohs hardness of 6.5–7 and a waxy to vitreous luster, usually purple, green or blue.
How can you tell amethyst from grape agate?
Amethyst grows as pointed crystals, not spheres.
Could you tell them apart from a blurry close-up?
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