Agate vs jasper: how to tell them apart
Updated . Based on the National Park Service, Oregon’s geology agency and the Mineralogical Society of America; sources are at the end.
Agate is translucent chalcedony with bands; jasper is opaque silica, usually mottled and often red. Both are forms of quartz with the same hardness and weight, so a scratch test will not separate them. Hold the stone against a strong light: agate lets some light through, jasper does not.
- Agate
- Translucent, banded, waxy to glassy
- Jasper
- Opaque, mottled, dull
- Same in both
- Hardness 7, specific gravity 2.65
- Color
- Not a reliable test
Side by side
| Agate | Jasper | |
|---|---|---|
| What it is | Translucent chalcedony | Opaque impure silica |
| Light through it | Yes, at least partly | No |
| Pattern | Bands, in rings or intricate patterns | Mottled |
| Luster | Waxy to glassy | Dull |
| Color | Varies a lot within one stone | Often red; also yellow, brown, green or blue |
| Hardness | 7 | 7 |
| Specific gravity | 2.65 | 2.65 |
Definitions from the National Park Service; pattern from Oregon’s geology agency and the Mineralogical Society of America; luster, hardness and specific gravity from the Society’s key. Jasper’s colors differ between the three sources.
The light test
Agate is translucent and jasper is opaque, so light is the clearest way to tell them apart. Hold the stone against a strong light or the sun and look at the thinner edges: if some light comes through, it points to agate. That is our tip, following from the definitions; no source we read gives a thickness at which agate starts to glow.
What does not help
- Scratching: both have a hardness of 7, so both scratch glass and resist a knife.
- Weight: both have a specific gravity of 2.65.
- Color: agate varies within one stone, and sources list jasper in red, yellow, brown, green and blue.
- Bands alone: no source we read says jasper is never banded, so check the light too.
Are they the same mineral?
Both are silica, the quartz family. The sources word it differently: Oregon’s geology agency calls both chalcedony, the National Park Service lists jasper separately as opaque impure silica, and the Mineralogical Society of America groups jasper with flint and chert. Both also occur in petrified wood, where the Park Service lists chalcedony, agate and jasper among the forms of silica that replace or fill it.
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Questions
What is the difference between agate and jasper?
Agate is translucent and banded; jasper is opaque and usually mottled. In the Mineralogical Society of America’s key, agate has a waxy to glassy luster and jasper a dull one.
Are agate and jasper the same mineral?
Both are forms of silica in the quartz family. Oregon’s geology agency calls both chalcedony, while the National Park Service lists jasper separately, as opaque impure silica.
How can I tell them apart at home?
Hold the stone against a strong light. Agate lets some light through; jasper does not.
Does a scratch test help?
No. The Mineralogical Society of America gives both a hardness of 7, so a knife or glass test gives the same result for both.
What colors are agate and jasper?
Agate varies a lot within one stone. Jasper is often red, according to the National Park Service, and also yellow, brown or green, or blue, depending on the source. Color alone will not tell them apart.
Can both be found in petrified wood?
Yes. The National Park Service lists chalcedony, agate and jasper among the forms of silica that can replace or fill wood.
