RocksdayGranite vs Pegmatite
How to tell them apart
A coarse-grained rock that cooled slowly deep underground, made of quartz, feldspar and mica or hornblende.
Photo: The stone gate, CC BY-SA 4.0
Granite with giant crystals — centimeters to meters across — formed from water-rich final melts.
Photo: No machine-readable author provided. Zimbres assumed (based on copyright claims)., CC BY-SA 2.5
Key differences
- Granite has the same minerals but much smaller grains.
Side by side
| Property | Granite | Pegmatite |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 6–7 | 6–7 |
| Luster | Granular, sparkly | Granular, glassy |
| Colors | Pink, Gray, White, Black | Pink, White, Gray, Black |
| Crystal system / structure | Coarse-grained (phaneritic) | Very coarse-grained |
| Specific gravity | 2.63–2.75 | 2.6–2.7 |
| Found in | Sierra Nevada, California; Stone Mountain, Georgia | Black Hills, South Dakota; Maine |
Properties that are the same for both are grayed out.
How to identify granite
- Speckled with interlocking grains you can see without a lens.
- Glassy gray quartz plus pink or white blocky feldspar.
- Black specks of mica or hornblende.
- Hard, with no layering or banding.
Structure: Coarse-grained (phaneritic)
Full Granite guide →How to identify pegmatite
- Huge interlocking crystals of feldspar, quartz and mica.
- May host tourmaline, beryl or garnet.
- Often in veins cutting other rocks.
Structure: Very coarse-grained
Full Pegmatite guide →More comparisons
Could you tell them apart from a blurry close-up?
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