Comparison · Igneous Rocks
Diorite vs Gabbro
Diorite and Gabbro are easy to confuse because both are igneous rocks. Both sit near Mohs 6–7, 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 Diorite and Gabbro
- Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- They overlap in gray, black, white, and multicolored, but Gabbro also comes in green.
Diorite vs Gabbro properties
| Property | Diorite | Gabbro |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6–7 | 5–6.5 |
| Luster | Vitreous to dull (granular) | Dull to vitreous (in crystals) |
| Transparency | Opaque | Opaque |
| Specific gravity | 2.8–3.0 | 2.9–3.1 |
| Common colors | Salt-and-pepper gray, Dark gray, Black and white speckled | Dark gray, Black, Greenish black, Speckled black and white |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Diorite and Gabbro trade in a similar range, around $10.
About Diorite
Diorite is a coarse-grained, intrusive igneous rock of intermediate composition, made mostly of plagioclase feldspar and dark hornblende or biotite, with little to no quartz. Its classic 'salt and pepper' look comes from the contrast between light gray-white feldspar and black amphibole crystals visible to the naked eye. It crystallizes slowly underground, giving it a fully crystalline, phaneritic texture.
About Gabbro
Gabbro is a coarse-grained, dark-colored intrusive igneous rock composed mainly of calcium-rich plagioclase feldspar and pyroxene, with the plutonic equivalent of basalt. It forms deep underground where mafic magma cools slowly enough for its mineral grains to grow large and interlock visibly. Its dense, speckled black-and-white texture makes it a popular dimension stone sold commercially as black granite.
Diorite vs Gabbro FAQ
Is Diorite the same as Gabbro?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Diorite from Gabbro?
Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. They overlap in gray, black, white, and multicolored, but Gabbro also comes in green.
Which is harder, Diorite or Gabbro?
Diorite is harder: Mohs 6–7 against Mohs 5–6.5 for Gabbro.
Which is more valuable, Diorite or Gabbro?
Typical specimens of Diorite and Gabbro trade in a similar range, around $10.
