Comparison · Metamorphic Rocks
Blueschist vs Mylonite
Blueschist and Mylonite are easy to confuse because both are metamorphic rocks. Both sit near Mohs 5.5, 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 Blueschist and Mylonite
- Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Blueschist leaves a variable; usually pale gray streak on unglazed porcelain, Mylonite leaves variable by mineral content.
- They overlap in gray, green, and black, but Blueschist also comes in blue and Mylonite also comes in white and brown.
Blueschist vs Mylonite properties
| Property | Blueschist | Mylonite |
|---|---|---|
| Type | Metamorphic Rocks | Metamorphic Rocks |
| Mohs hardness | 5.5 | 5.5 |
| Luster | silky | silky |
| Streak | Variable; usually pale gray | Variable by mineral content |
| Transparency | opaque | opaque |
| Specific gravity | 3.1 | 2.7 |
| Crystal system | varies | varies |
| Common colors | Blue, Blue gray, Gray, Green, Black | Gray, Black, White, Green, Brown |
| Rarity | uncommon | uncommon |
| Typical specimen value | $5–$150+ | $1–$75+ |
Which is more valuable?
Blueschist is usually the more valuable of the two: a typical collector specimen runs about $30 against $10 for Mylonite, and premium Blueschist can reach $150 or more.
About Blueschist
Blueschist is a blue to blue-gray metamorphic rock linked to subduction zones. Its color often comes from blue amphibole minerals such as glaucophane.
About Mylonite
Mylonite is a fine-grained, streaky metamorphic rock formed by intense ductile shearing in fault zones. It can show stretched mineral bands and a strong fabric.
Blueschist vs Mylonite FAQ
Is Blueschist the same as Mylonite?
No. Both are metamorphic rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Blueschist from Mylonite?
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Blueschist leaves a variable; usually pale gray streak on unglazed porcelain, Mylonite leaves variable by mineral content. They overlap in gray, green, and black, but Blueschist also comes in blue and Mylonite also comes in white and brown.
Which is harder, Blueschist or Mylonite?
They are about equally hard, both near Mohs 5.5.
Which is more valuable, Blueschist or Mylonite?
Blueschist is usually the more valuable of the two: a typical collector specimen runs about $30 against $10 for Mylonite, and premium Blueschist can reach $150 or more.
