Crystal & mineral guide
Limestone
Sedimentary carbonate rock
Calcite-dominated sedimentary rock — cement feedstock and fossil archive.
Identify Limestone with RockScanAbout Limestone
Limestone is chiefly calcite, often fossiliferous. Fizzes strongly in dilute acid. Foundation of cement industry and common building stone. Middle East carbonate platforms are world-class petroleum reservoirs. Metamorphoses to marble.
Limestone belongs in a crystal identifier workflow because photo cues — color zoning, crystal habit, and surface luster — combine with measurable traits like Mohs 3–4 (aggregate) and specific gravity 2.3–2.7. Use RockScan’s camera to get a first-pass ID, then confirm with the checklist below.
Limestone properties
| Mohs hardness | 3–4 (aggregate) |
|---|---|
| Crystal system | Carbonate aggregate |
| Luster | Dull to earthy |
| Color | White, gray, tan, fossiliferous |
| Composition | Primarily calcite (CaCO₃) |
| Formation | Marine chemical/biogenic carbonate deposition |
| Occurrence | Worldwide; extensive Middle East carbonate platforms |
| Specific gravity | 2.3–2.7 |
| Cleavage | None (rock) |
How to identify Limestone
- Strong acid fizz
- May show fossils
- Softer than sandstone/silicates
Collector notes
- Cement manufacture consumes vast limestone tonnage
- Karst landscapes dissolve from limestone terrains
Value context: Industrial chemical/aggregate rock; fossiliferous slabs for décor.
Limestone FAQ
How do you identify Limestone?
Limestone (Sedimentary carbonate rock) is typically recognized by white, gray, tan, fossiliferous color, dull to earthy luster, Mohs hardness 3–4 (aggregate), and carbonate aggregate crystal system. RockScan can suggest Limestone from a photo and surface these checks on the result card.
What is Limestone made of?
Limestone composition: Primarily calcite (CaCO₃). It forms via marine chemical/biogenic carbonate deposition and is found in Worldwide; extensive Middle East carbonate platforms.
Is Limestone valuable?
Industrial chemical/aggregate rock; fossiliferous slabs for décor.
