Sedimentary Rocks · common
Limestone
Limestone is a sedimentary rock composed mainly of calcium carbonate. It often contains fossils and is the precursor to marble.
Also known as: calcium carbonate, fossil bearing.
Limestone properties at a glance
| Type | Sedimentary Rocks |
|---|---|
| Chemical formula | CaCO3 |
| Mohs hardness | 3 |
| Luster | dull |
| Streak | White |
| Cleavage | Variable by mineral grains |
| Fracture | Conchoidal |
| Specific gravity | 2.7 |
| Transparency | opaque |
| Common colors | White, Gray, Tan, Yellow |
| Rarity | common |
Geology & background
Forms from accumulation of marine organism shells and skeletal fragments, or by chemical precipitation from seawater.
Primary building material for ancient civilizations including the Egyptians, Greeks, and Romans.
How to identify Limestone
- Check whether the specimen's color and texture match typical Limestone examples.
- Photograph a fresh surface in natural light and avoid shadows, glare, or wet surfaces.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Full Limestone identification guide: checklist, home tests and look-alikes →
Limestone vs similar stones
Not sure it isn't something else? Side-by-side comparisons with the stones most often confused with Limestone.
Where Limestone is found
Limestone is reported from multiple localities or geological settings. Exact locality should be verified from specimen provenance, maps, or field notes.
How much is Limestone worth?
| Entry-level specimen | $1 |
|---|---|
| Typical collector specimen | $10 |
| Premium specimen | $50+ |
Value depends on size, condition, color, crystal quality, locality, rarity, preparation, and provenance. Treat this as educational guidance, not an appraisal.
Common uses
- Cement production
- Building stone
- Agriculture
- Steel production
Interesting facts
- The Great Pyramid of Giza was originally covered in white limestone
- Forms caves through dissolution, creating stalactites and stalagmites
- Source of lime used in cement production
Care & safety
Treat Limestone as a collector specimen unless hardness, cleavage, and fracture are confirmed.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a properly rated respirator.
Limestone FAQ
What is Limestone?
Limestone is a sedimentary rock composed mainly of calcium carbonate. It often contains fossils and is the precursor to marble.
How much is Limestone worth?
Entry-level Limestone specimens sell for around $1, a typical collector specimen for about $10, and premium pieces for $50 or more. Value depends on size, condition, color, crystal quality, locality, rarity, preparation, and provenance. Treat this as educational guidance, not an appraisal.
How hard is Limestone?
Limestone has a Mohs hardness of 3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
Where is Limestone found?
Notable sources of Limestone include USA, UK, Germany, and China. Forms from accumulation of marine organism shells and skeletal fragments, or by chemical precipitation from seawater..
What is Limestone used for?
Limestone is used for cement production, building stone, agriculture, and steel production.
