Comparison · Igneous Rocks
Diabase vs Rainbow Obsidian
Diabase and Rainbow Obsidian 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 Diabase and Rainbow Obsidian
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Diabase leaves a variable; test individual minerals streak on unglazed porcelain, Rainbow Obsidian leaves white.
- Luster is different: Diabase is varies while Rainbow Obsidian is vitreous.
- They overlap in multicolored, but Rainbow Obsidian also comes in black, purple, green, and yellow.
Diabase vs Rainbow Obsidian properties
| Property | Diabase | Rainbow Obsidian |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 5.5 |
| Luster | varies | vitreous |
| Streak | Variable; test individual minerals | White |
| Transparency | opaque | opaque |
| Specific gravity | 2.8 | 2.4 |
| Crystal system | varies | amorphous |
| Common colors | Various | Black with rainbow sheen, Purple, Green, Gold |
| Rarity | common | uncommon |
| Typical specimen value | $1–$75+ | $10–$200+ |
Which is more valuable?
Rainbow Obsidian is usually the more valuable of the two: a typical collector specimen runs about $50 against $10 for Diabase, and premium Rainbow Obsidian can reach $200 or more.
About Diabase
Diabase is a dark, medium-grained mafic igneous rock, also called dolerite in many regions. It commonly forms in dikes and sills and sits texturally between basalt and gabbro.
About Rainbow Obsidian
Rainbow obsidian is a type of volcanic glass that displays bands of colorful iridescence when polished and viewed in bright light.
Diabase vs Rainbow Obsidian FAQ
Is Diabase the same as Rainbow Obsidian?
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 Diabase from Rainbow Obsidian?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Diabase leaves a variable; test individual minerals streak on unglazed porcelain, Rainbow Obsidian leaves white. Luster is different: Diabase is varies while Rainbow Obsidian is vitreous.
Which is harder, Diabase or Rainbow Obsidian?
Diabase is harder: Mohs 6 against Mohs 5.5 for Rainbow Obsidian.
Which is more valuable, Diabase or Rainbow Obsidian?
Rainbow Obsidian is usually the more valuable of the two: a typical collector specimen runs about $50 against $10 for Diabase, and premium Rainbow Obsidian can reach $200 or more.
