Comparison · Igneous Rocks
Basalt vs Monzonite
Basalt and Monzonite 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 Basalt and Monzonite
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Monzonite leaves variable; usually light gray.
- They overlap in black, gray, and green, but Monzonite also comes in pink and white.
Basalt vs Monzonite properties
| Property | Basalt | Monzonite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 6 |
| Luster | dull | dull |
| Streak | Variable; test individual minerals | Variable; usually light gray |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.75 |
| Crystal system | varies | varies |
| Common colors | Black, Dark Gray, Dark Green | Gray, Pink, White, Black, Greenish gray |
| Rarity | common | common |
| Typical specimen value | $1–$30+ | $1–$75+ |
Which is more valuable?
Monzonite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Monzonite can reach $75 or more.
About Basalt
Basalt is a dark, fine-grained volcanic rock that makes up most of the ocean floor and Hawaiian Islands. It often forms distinctive columnar jointing.
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.
Basalt vs Monzonite FAQ
Is Basalt the same as Monzonite?
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 Basalt from Monzonite?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Monzonite leaves variable; usually light gray. They overlap in black, gray, and green, but Monzonite also comes in pink and white.
Which is harder, Basalt or Monzonite?
They are about equally hard, both near Mohs 6.
Which is more valuable, Basalt or Monzonite?
Monzonite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Monzonite can reach $75 or more.
