RocksdayMonzonite vs Syenite
How to tell them apart
A coarse rock with roughly equal pink alkali feldspar and white plagioclase, and little quartz.
Photo: Courtesy NASA/JPL-Caltech, Public domain
Looks like granite but has little or no quartz; mostly alkali feldspar.
Photo: James St. John, CC BY 2.0
Key differences
- Syenite is mostly alkali feldspar.
- Monzonite has more white plagioclase.
Side by side
| Property | Monzonite | Syenite |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 6 | 6 |
| Luster | Granular | Granular |
| Colors | Gray, Pink, White | Pink, Gray, White |
| Crystal system / structure | Coarse-grained (phaneritic) | Coarse-grained (phaneritic) |
| Specific gravity | 2.7–2.8 | 2.6–2.8 |
| Found in | Monzoni, Italy; Bingham Canyon, Utah | Magnet Cove, Arkansas; Ontario, Canada |
Properties that are the same for both are grayed out.
How to identify monzonite
- Mix of pink and white feldspar.
- Some dark minerals, little quartz.
- Coarse, even grains.
Structure: Coarse-grained (phaneritic)
Full Monzonite guide →How to identify syenite
- Coarse pink or gray feldspar crystals.
- Little or no glassy quartz.
- Some dark hornblende or biotite.
Structure: Coarse-grained (phaneritic)
Full Syenite guide →More comparisons
Could you tell them apart from a blurry close-up?
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