Comparison · Igneous Rocks
Monzonite vs Syenite
Monzonite and Syenite are easy to confuse because both are igneous rocks. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Monzonite and Syenite
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Luster is different: Monzonite is dull while Syenite is vitreous (feldspar crystals).
- Hold a thin edge to the light: Monzonite is opaque, Syenite is Opaque.
- They overlap in gray, pink, white, and green, but Monzonite also comes in black.
Monzonite vs Syenite properties
| Property | Monzonite | Syenite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 5.5–6.5 |
| Luster | dull | Vitreous (feldspar crystals) |
| Streak | Variable; usually light gray | — |
| Transparency | opaque | Opaque |
| Specific gravity | 2.75 | 2.6–2.8 |
| Crystal system | varies | — |
| Common colors | Gray, Pink, White, Black, Greenish gray | Gray, Pink, White, Light green |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Monzonite and Syenite trade in a similar range, around $10.
About Monzonite
Monzonite is a coarse-grained intrusive igneous rock with roughly balanced alkali feldspar and plagioclase and little quartz. It can resemble granite or diorite in hand sample.
About Syenite
Syenite is a coarse-grained intrusive igneous rock composed mainly of alkali feldspar with minor amounts of dark minerals like hornblende or biotite, and it is distinguished from granite chiefly by containing little to no quartz. It forms from the slow cooling of silica-undersaturated to silica-saturated magmas at depth, allowing large, visible crystals to develop. Syenite's name derives from Syene, the ancient name for Aswan, Egypt, though the rock originally described there under that name is now known to actually be granite.
Monzonite vs Syenite FAQ
Is Monzonite the same as Syenite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Monzonite from Syenite?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Luster is different: Monzonite is dull while Syenite is vitreous (feldspar crystals). Hold a thin edge to the light: Monzonite is opaque, Syenite is Opaque.
Which is harder, Monzonite or Syenite?
They are about equally hard, both near Mohs 6.
Which is more valuable, Monzonite or Syenite?
Typical specimens of Monzonite and Syenite trade in a similar range, around $10.
