Identification guide · Igneous Rocks
How to Identify Monzonite
Monzonite is usually gray, pink, and white with a dull luster and is opaque. It 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. Its streak is variable; usually light gray. It is most often confused with Tonalite, Aplite, and Granite; the tests below separate them.
Monzonite identification checklist
| Color | Gray, Pink, White, Black, Greenish gray | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Dull | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Variable; usually light gray | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Variable by feldspar grains | |
| Fracture | Uneven to granular | |
| Specific gravity | 2.75 | Ordinary rock-like heft (specific gravity about 2.75), similar to quartz. |
Monzonite look-alikes and how to tell them apart
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Monzonite vs Tonalite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Monzonite vs Aplite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Monzonite vs Granite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Monzonite vs Granodiorite →
Field tips
- 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.
Monzonite identification FAQ
How can you tell if a rock is Monzonite?
Check the color (gray, pink, white, and black), the dull luster, a Mohs hardness of 6 and a variable; usually light gray streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of 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 the difference between Monzonite and Tonalite?
Monzonite (Mohs 6, dull luster) and Tonalite (Mohs 6, dull luster) look alike, but hardness, streak and heft usually separate them. See the full Monzonite vs Tonalite comparison for a side-by-side table.
Is Monzonite worth anything?
Entry-level Monzonite specimens sell for around $1, typical collector pieces about $10, and premium examples $75 or more depending on size, quality and locality.
What color is Monzonite?
Monzonite is most often gray, pink, white, and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
