Comparison · Metamorphic Rocks
Mylonite vs Soapstone
Mylonite and Soapstone are easy to confuse because both are metamorphic rocks. Mylonite is harder (Mohs 5.5) than Soapstone (Mohs 1–2.5), so Mylonite will scratch Soapstone and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Mylonite and Soapstone
- Mylonite is harder (Mohs 5.5) than Soapstone (Mohs 1–2.5), so Mylonite will scratch Soapstone and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
- Streak color differs: Mylonite leaves a variable by mineral content streak on unglazed porcelain, Soapstone leaves white.
- Hold a thin edge to the light: Mylonite is opaque, Soapstone is Opaque.
- They overlap in gray, white, and green, but Mylonite also comes in black and brown.
Mylonite vs Soapstone properties
| Property | Mylonite | Soapstone |
|---|---|---|
| Type | Metamorphic Rocks | Metamorphic Rocks |
| Mohs hardness | 5.5 | 1–2.5 |
| Luster | silky | Greasy to pearly/waxy |
| Streak | Variable by mineral content | White |
| Transparency | opaque | Opaque |
| Specific gravity | 2.7 | 2.6–2.8 |
| Crystal system | varies | — |
| Common colors | Gray, Black, White, Green, Brown | Gray, Green, White, Bluish gray |
| Rarity | uncommon | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Mylonite and Soapstone trade in a similar range, around $10.
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.
About Soapstone
Soapstone, also called steatite, is a soft metamorphic rock composed predominantly of talc along with varying amounts of chlorite, mica, amphiboles, and carbonate minerals. Its defining trait is an extremely low hardness, around 1 on the Mohs scale, giving it the greasy, soap-like feel that inspired its common name. It forms through the metamorphism of ultramafic and other magnesium-rich rocks, often near serpentinite bodies.
Mylonite vs Soapstone FAQ
Is Mylonite the same as Soapstone?
No. Both are metamorphic rocks, but they are distinct rock types with different hardness, streak or luster. Mylonite is harder (Mohs 5.5) than Soapstone (Mohs 1–2.5), so Mylonite will scratch Soapstone and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Mylonite from Soapstone?
Mylonite is harder (Mohs 5.5) than Soapstone (Mohs 1–2.5), so Mylonite will scratch Soapstone and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Streak color differs: Mylonite leaves a variable by mineral content streak on unglazed porcelain, Soapstone leaves white. Hold a thin edge to the light: Mylonite is opaque, Soapstone is Opaque.
Which is harder, Mylonite or Soapstone?
Mylonite is harder: Mohs 5.5 against Mohs 1–2.5 for Soapstone.
Which is more valuable, Mylonite or Soapstone?
Typical specimens of Mylonite and Soapstone trade in a similar range, around $10.
