Comparison · Quartz Family vs Minerals
Agate vs Chalcedony
Agate and Chalcedony are easy to confuse. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Agate and Chalcedony
- Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Luster is different: Agate is waxy while Chalcedony is waxy to vitreous.
- Hold a thin edge to the light: Agate is translucent, Chalcedony is Translucent.
- They overlap in multicolored, blue, brown, and gray, but Agate also comes in red and green and Chalcedony also comes in white.
- Well-formed crystals give it away: Agate is hexagonal, Chalcedony is Trigonal (cryptocrystalline).
Agate vs Chalcedony properties
| Property | Agate | Chalcedony |
|---|---|---|
| Type | Quartz Family | Minerals |
| Mohs hardness | 7 | 6.5–7 |
| Luster | waxy | Waxy to vitreous |
| Streak | White | White |
| Transparency | translucent | Translucent |
| Specific gravity | 2.6 | 2.6–2.64 |
| Crystal system | hexagonal | Trigonal (cryptocrystalline) |
| Common colors | Banded, Blue, Brown, Red, Green, Gray | Blue-gray, White, Brown, Various (often dyed) |
| Rarity | common | common |
| Typical specimen value | $5–$300+ | $2–$150+ |
Which is more valuable?
Agate is usually the more valuable of the two: a typical collector specimen runs about $25 against $20 for Chalcedony, and premium Agate can reach $300 or more.
About Agate
Agate is a banded variety of chalcedony formed in concentric layers in volcanic rocks. Each layer represents a different period of mineral deposition.
About Chalcedony
Chalcedony is a cryptocrystalline form of quartz made of microscopic fibrous crystals too small to resolve without magnification, chemically identical to ordinary quartz but structurally distinct from it. It serves as the parent material for a large family of banded and colored varieties, including agate, onyx, carnelian, and chrysoprase. Chalcedony typically forms a waxy, translucent to semi-translucent mass rather than distinct visible crystals.
Agate vs Chalcedony FAQ
Is Agate the same as Chalcedony?
No. Agate is a quartz family while Chalcedony is a mineral. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Agate from Chalcedony?
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Luster is different: Agate is waxy while Chalcedony is waxy to vitreous. Hold a thin edge to the light: Agate is translucent, Chalcedony is Translucent.
Which is harder, Agate or Chalcedony?
They are about equally hard, both near Mohs 7.
Which is more valuable, Agate or Chalcedony?
Agate is usually the more valuable of the two: a typical collector specimen runs about $25 against $20 for Chalcedony, and premium Agate can reach $300 or more.
