Crystals That Look Like Marble
Marble is a metamorphic rock made mostly of calcite — soft (Mohs 3), often white with veining, and it fizzes in dilute acid. Several pale, veined stones get mistaken for it. Two field tests sort most of them out: hardness (a steel knife scratches soft carbonates) and the acid test (carbonates fizz; silica look-alikes don't).
Marble look-alikes at a glance
| Stone | Hardness | How to tell it from marble |
|---|---|---|
| Marble | — | Marble itself: metamorphosed limestone, mostly calcite — Mohs 3, scratched by a knife, fizzes in dilute acid. |
| Calcite | Mohs 3 | The mineral marble is largely made of (Mohs 3); rhombic cleavage and a strong fizz in acid. |
| Onyx | Mohs 6.5–7 | True onyx is banded chalcedony (Mohs ~7, won't scratch). But "onyx marble" sold for carvings is actually banded calcite — soft and fizzes in acid. |
| Howlite | Mohs 3.5 | Chalky white with grey "marble" veining; very soft (Mohs 3.5) and often dyed to imitate turquoise. |
| Magnesite | Mohs 3.5–4.5 | White and porcelain-like; a carbonate like marble but it won't fizz in cold acid the way calcite does. |
| Dolomite | Mohs 3.5–4.0 | Close to calcite but slightly harder (~4) and only fizzes in warm or powdered acid. |
| Selenite | Mohs 2 | Translucent gypsum (alabaster) is carved like marble but is far softer (Mohs 2) — a fingernail scratches it. |
See the photos
Frequently asked questions
How can you tell marble from a look-alike stone?
Marble is soft (Mohs 3) and a carbonate, so a steel knife scratches it and a drop of dilute acid (even vinegar) makes it fizz. Harder look-alikes such as quartzite or true onyx (chalcedony) won't scratch or fizz; softer ones like alabaster (gypsum) scratch with a fingernail.
Is marble a crystal?
Marble is a rock, not a single crystal — it is metamorphosed limestone made of interlocking calcite (or dolomite) crystals. That granular crystalline structure is why it polishes to a glow but stays soft enough to scratch.