RocksdayOolite vs Sandstone
How to tell them apart
Limestone made of tiny round grains that look like fish eggs.
Photo: Wilson44691, Public domain
Sand grains — mostly quartz — cemented together. Many sandstones preserve ancient beaches, rivers or desert dunes.
Photo: Unknown, Public domain
Quick tests
- Scratch glass: Sandstone scratches glass (Mohs 6–7); Oolite can't (Mohs 3–4).
- Acid (vinegar or dilute HCl): Oolite fizzes; Sandstone doesn't.
Key differences
- Sandstone grains are quartz and don't fizz.
Side by side
| Property | Oolite | Sandstone |
|---|---|---|
| Type | Sedimentary rock | Sedimentary rock |
| Mohs hardness | 3–4 | 6–7 |
| Luster | Dull | Dull, gritty |
| Colors | White, Yellow, Gray | Brown, Red, Yellow, White, Orange |
| Crystal system / structure | Tiny spherical grains (ooids) | Clastic, sand-sized grains |
| Specific gravity | 2.4–2.7 | 2.2–2.8 |
| Found in | Bath, England; The Bahamas | Zion and Arches, Utah; Petra, Jordan |
Properties that are the same for both are grayed out.
How to identify oolite
- Packed with sand-sized spheres.
- Creamy color.
- Fizzes in acid.
Structure: Tiny spherical grains (ooids)
Full Oolite guide →How to identify sandstone
- Gritty, like sandpaper.
- Individual sand grains visible with a lens.
- Grains rub off when scraped.
- Often layered or cross-bedded.
Structure: Clastic, sand-sized grains
Full Sandstone guide →More comparisons
Could you tell them apart from a blurry close-up?
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