RocksdayChalcedony vs Grape Agate
To tell Chalcedony from Grape Agate: Ordinary chalcedony is a smooth crust, not a cluster of separate balls.
Quartz made of microscopic fibers. Plain chalcedony is soft blue-gray and often grows in bubbly, grape-like crusts.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
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
- Ordinary chalcedony is a smooth crust, not a cluster of separate balls.
Side by side
| Property | Chalcedony | Grape Agate |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 6.5–7 | 6.5–7 |
| Luster | Waxy | Waxy to vitreous |
| Streak | White | White |
| Colors | Blue, White, Gray | Purple, Green, Blue |
| Crystal system | Microcrystalline quartz | Botryoidal quartz |
| Specific gravity | 2.58–2.64 | 2.6–2.65 |
| Formula | SiO₂ | SiO₂ |
| Found in | Oregon; Namibia | West Sulawesi, Indonesia |
Properties that are the same for both are grayed out.
How to identify chalcedony
- Waxy, translucent and milky.
- Bubbly 'botryoidal' surfaces are common.
- No crystal faces; scratches glass.
Crystal system: Microcrystalline quartz
Full Chalcedony 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 chalcedony and grape agate?
Chalcedony is a mineral (SiO₂) with a Mohs hardness of 6.5–7 and a waxy luster, usually blue, white or gray. 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 chalcedony from grape agate?
Ordinary chalcedony is a smooth crust, not a cluster of separate balls.
Could you tell them apart from a blurry close-up?
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