Identification guide · Metamorphic Rocks
How to Identify Marble
Marble is usually white, gray, and pink with a vitreous luster and is translucent. It has a Mohs hardness of 3.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is white. It is most often confused with Feldspar, Quartz, and Schist; the tests below separate them.
Marble identification checklist
| Color | White, Gray, Pink, Green, Black | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 3.5 | A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Variable by mineral grains | |
| Fracture | Granular | |
| Specific gravity | 2.7 | Ordinary rock-like heft (specific gravity about 2.7), similar to quartz. |
Extra tests for Marble
Acid test. Fizzes in vinegar or dilute hydrochloric acid because of its carbonate content.
Marble look-alikes and how to tell them apart
Feldspar is harder (Mohs 6–6.5) than Marble (Mohs 3.5), so Feldspar will scratch Marble and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Marble vs Feldspar →
Quartz is harder (Mohs 7) than Marble (Mohs 3.5), so Quartz will scratch Marble and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Marble vs Quartz →
Schist is harder (Mohs 2.5–7) than Marble (Mohs 3.5), so Schist will scratch Marble and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Marble vs Schist →
Marble is harder (Mohs 3.5) than Brucite (Mohs 2.5), so Marble will scratch Brucite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
Field tips
- Check whether the specimen's color and texture match typical Marble examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Marble identification FAQ
How can you tell if a rock is Marble?
Check the color (white, gray, pink, and green), the vitreous luster, a Mohs hardness of 3.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Marble?
Marble has a Mohs hardness of 3.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Marble and Feldspar?
Marble (Mohs 3.5, vitreous luster) and Feldspar (Mohs 6–6.5, vitreous to pearly luster) look alike, but hardness, streak and heft usually separate them. See the full Marble vs Feldspar comparison for a side-by-side table.
Is Marble worth anything?
Entry-level Marble specimens sell for around $5, typical collector pieces about $50, and premium examples $500 or more depending on size, quality and locality.
What color is Marble?
Marble is most often white, gray, pink, and green. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
