RocksdayConglomerate vs Metaconglomerate
How to tell them apart
Rounded pebbles and cobbles glued together by finer sand and cement — a fossil riverbed or beach.
Photo: James St. John, CC BY 2.0
Conglomerate squeezed by metamorphism until its pebbles stretched and flattened.
Photo: Wilson44691, Public domain
Key differences
- Conglomerate pebbles are round and pop out.
Side by side
| Property | Conglomerate | Metaconglomerate |
|---|---|---|
| Type | Sedimentary rock | Metamorphic rock |
| Mohs hardness | 5–7 | 6–7 |
| Luster | Dull | Granular |
| Colors | Brown, Gray, Red | Gray, White, Brown |
| Crystal system / structure | Clastic, rounded pebbles in matrix | Stretched, flattened pebbles |
| Specific gravity | 2.4–2.7 | 2.6–2.8 |
| Found in | Montserrat, Spain; Kata Tjuta, Australia | Rhode Island; Norway |
Properties that are the same for both are grayed out.
How to identify conglomerate
- Contains rounded pebbles larger than 2 mm.
- Pebbles of different rock types.
- Sand or mud fills the gaps.
- Looks like natural concrete.
Structure: Clastic, rounded pebbles in matrix
Full Conglomerate guide →How to identify metaconglomerate
- Elongated, flattened pebbles all pointing the same way.
- Hard; breaks through pebbles.
- Pebbles often quartzite.
Structure: Stretched, flattened pebbles
Full Metaconglomerate guide →More comparisons
Could you tell them apart from a blurry close-up?
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