Comparison · Igneous Rocks
Diorite vs Pegmatite
Diorite and Pegmatite 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 Pegmatite
- Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Diorite is Opaque, Pegmatite is Opaque (individual crystals may be transparent).
- They overlap in gray, white, and multicolored, but Diorite also comes in black and Pegmatite also comes in pink.
Diorite vs Pegmatite properties
| Property | Diorite | Pegmatite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6–7 | 6–7 |
| Luster | Vitreous to dull (granular) | Vitreous (large crystal faces) |
| Transparency | Opaque | Opaque (individual crystals may be transparent) |
| Specific gravity | 2.8–3.0 | 2.6–2.8 |
| Common colors | Salt-and-pepper gray, Dark gray, Black and white speckled | Pink, White, Gray, Multicolored (with tourmaline, etc.) |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Diorite and Pegmatite 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 Pegmatite
Pegmatite is an exceptionally coarse-grained igneous rock, typically granitic in composition, distinguished by crystals often several centimeters to meters in size, far larger than in ordinary granite. Its unusually large crystals result from crystallizing out of a water- and rare-element-enriched residual melt left over after most of a magma body has already solidified. Pegmatites serve as the primary source of many rare minerals and gemstones, including tourmaline, beryl, spodumene, and topaz.
Diorite vs Pegmatite FAQ
Is Diorite the same as Pegmatite?
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 Pegmatite?
Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Diorite is Opaque, Pegmatite is Opaque (individual crystals may be transparent). They overlap in gray, white, and multicolored, but Diorite also comes in black and Pegmatite also comes in pink.
Which is harder, Diorite or Pegmatite?
They are about equally hard, both near Mohs 6–7.
Which is more valuable, Diorite or Pegmatite?
Typical specimens of Diorite and Pegmatite trade in a similar range, around $10.
