RocksdayAplite vs Pegmatite
How to tell them apart
A pale, fine-grained, sugary granite that fills thin dikes cutting through other granites.
Photo: Lysippos, CC BY-SA 3.0
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
- Pegmatite has huge crystals.
Side by side
| Property | Aplite | Pegmatite |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 6–7 | 6–7 |
| Luster | Sugary | Granular, glassy |
| Colors | White, Pink | Pink, White, Gray, Black |
| Crystal system / structure | Fine-grained, sugary | Very coarse-grained |
| Specific gravity | 2.6–2.7 | 2.6–2.7 |
| Found in | Sierra Nevada, California; Granite regions worldwide | Black Hills, South Dakota; Maine |
Properties that are the same for both are grayed out.
How to identify aplite
- Thin white or pink veins with sharp edges.
- Fine, even, sugary grains.
- Very few dark minerals.
Structure: Fine-grained, sugary
Full Aplite 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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