Identification guide · Sedimentary Rocks
How to Identify Sandstone
Sandstone is usually tan, brown, and red with a dull luster and is opaque. It has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Its streak is variable; test individual minerals. It is most often confused with Arkose, Graywacke, and Quartz; the tests below separate them.
Sandstone identification checklist
| Color | Tan, Brown, Red, Yellow, White, Gray | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Dull | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Variable; test individual minerals | 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 | 2.3 | Ordinary rock-like heft (specific gravity about 2.3), similar to quartz. |
Sandstone look-alikes and how to tell them apart
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Sandstone vs Arkose →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Sandstone vs Graywacke →
Quartz is harder (Mohs 7) than Sandstone (Mohs 6), so Quartz will scratch Sandstone and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Sandstone vs Quartz →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Check whether the specimen's color and texture match typical Sandstone examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Sandstone identification FAQ
How can you tell if a rock is Sandstone?
Check the color (tan, brown, red, and yellow), the dull luster, a Mohs hardness of 6 and a variable; test individual minerals streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Sandstone?
Sandstone has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is the difference between Sandstone and Arkose?
Sandstone (Mohs 6, dull luster) and Arkose (Mohs 6, dull luster) look alike, but hardness, streak and heft usually separate them. See the full Sandstone vs Arkose comparison for a side-by-side table.
Is Sandstone worth anything?
Entry-level Sandstone specimens sell for around $1, typical collector pieces about $15, and premium examples $100 or more depending on size, quality and locality.
What color is Sandstone?
Sandstone is most often tan, brown, red, and yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
