Comparison · Sedimentary Rocks
Sandstone vs Siltstone
Sandstone and Siltstone are easy to confuse because both are sedimentary rocks. Sandstone is harder (Mohs 6) than Siltstone (Mohs 3.5), so Sandstone will scratch Siltstone and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Sandstone and Siltstone
- Sandstone is harder (Mohs 6) than Siltstone (Mohs 3.5), so Sandstone will scratch Siltstone and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Streak color differs: Sandstone leaves a variable; test individual minerals streak on unglazed porcelain, Siltstone leaves variable; often light gray to brown.
- They overlap in brown, red, and gray, but Sandstone also comes in yellow and white and Siltstone also comes in green.
Sandstone vs Siltstone properties
| Property | Sandstone | Siltstone |
|---|---|---|
| Type | Sedimentary Rocks | Sedimentary Rocks |
| Mohs hardness | 6 | 3.5 |
| Luster | dull | dull |
| Streak | Variable; test individual minerals | Variable; often light gray to brown |
| Transparency | opaque | opaque |
| Specific gravity | 2.3 | 2.45 |
| Crystal system | varies | varies |
| Common colors | Tan, Brown, Red, Yellow, White, Gray | Gray, Tan, Brown, Red, Green |
| Rarity | common | common |
| Typical specimen value | $1–$100+ | $1–$75+ |
Which is more valuable?
Sandstone is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Siltstone, and premium Sandstone can reach $100 or more.
About Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized mineral particles or rock fragments. Color varies based on mineral content and cementing material.
About Siltstone
Siltstone is a fine-grained sedimentary rock made mostly of silt-sized particles. It feels smoother than sandstone but grittier than claystone or shale.
Sandstone vs Siltstone FAQ
Is Sandstone the same as Siltstone?
No. Both are sedimentary rocks, but they are distinct rock types with different hardness, streak or luster. Sandstone is harder (Mohs 6) than Siltstone (Mohs 3.5), so Sandstone will scratch Siltstone and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Sandstone from Siltstone?
Sandstone is harder (Mohs 6) than Siltstone (Mohs 3.5), so Sandstone will scratch Siltstone and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Streak color differs: Sandstone leaves a variable; test individual minerals streak on unglazed porcelain, Siltstone leaves variable; often light gray to brown. They overlap in brown, red, and gray, but Sandstone also comes in yellow and white and Siltstone also comes in green.
Which is harder, Sandstone or Siltstone?
Sandstone is harder: Mohs 6 against Mohs 3.5 for Siltstone.
Which is more valuable, Sandstone or Siltstone?
Sandstone is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Siltstone, and premium Sandstone can reach $100 or more.
