Igneous Rocks · common
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.
Also known as: Quartz monzonite, Feldspar-rich intrusive rock.
Monzonite properties at a glance
| Type | Igneous Rocks |
|---|---|
| Chemical formula | Alkali feldspar and plagioclase-rich intrusive rock |
| Mohs hardness | 6 |
| Luster | dull |
| Streak | Variable; usually light gray |
| Cleavage | Variable by feldspar grains |
| Fracture | Uneven to granular |
| Specific gravity | 2.75 |
| Transparency | opaque |
| Common colors | Gray, Pink, White, Black, Greenish gray |
| Rarity | common |
Geology & background
Forms when magma cools slowly underground, producing coarse feldspar-rich crystals with relatively little quartz.
Monzonite helps geologists classify intrusive rocks and understand slowly cooled magma bodies.
How to identify Monzonite
- Look for coarse feldspar-rich texture with less quartz than granite.
- Pink and white feldspar mixed with dark minerals can resemble granite.
- Monzonite is usually more feldspar-balanced than syenite or diorite.
- A close photo of grains helps separate it from granite, diorite, and granodiorite.
Full Monzonite identification guide: checklist, home tests and look-alikes →
Monzonite vs similar stones
Not sure it isn't something else? Side-by-side comparisons with the stones most often confused with Monzonite.
Where Monzonite is found
Reported from multiple igneous terrains worldwide; verify locality against specimen provenance when available.
How much is Monzonite worth?
| Entry-level specimen | $1 |
|---|---|
| Typical collector specimen | $10 |
| Premium specimen | $75+ |
Monzonite is usually valued for teaching, field context, locality, texture, color, mineral content, or unusually attractive specimens rather than high gem value.
Common uses
- Field identification
- Education
- Decorative stone
- Intrusive rock comparison
Interesting facts
- Monzonite sits compositionally between syenite and diorite.
- Quartz is usually minor compared with true granite.
- Some decorative building stones are monzonitic or related rocks.
Care & safety
Monzonite can vary in toughness, porosity, vesicles, glass content, and weathering depending on cooling history and mineral mix.
Avoid inhaling dust. Do not cut, grind, or polish unknown igneous rocks without eye protection and a properly rated respirator.
Monzonite FAQ
What is 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.
How much is Monzonite worth?
Entry-level Monzonite specimens sell for around $1, a typical collector specimen for about $10, and premium pieces for $75 or more. Monzonite is usually valued for teaching, field context, locality, texture, color, mineral content, or unusually attractive specimens rather than high gem value.
How hard is Monzonite?
Monzonite has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is Monzonite used for?
Monzonite is used for field identification, education, decorative stone, and intrusive rock comparison.
