Identification guide · Sedimentary Rocks
How to Identify Rock Salt
Rock Salt is usually clear, white, and pink with a vitreous luster and is opaque. It has a Mohs hardness of 2.5. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Its streak is white. It is most often confused with Halite, Anhydrite, and Gypsum; the tests below separate them.
Rock Salt identification checklist
| Color | Clear, White, Pink, Orange, Gray | 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 | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 2.5 | A copper coin (Mohs 3.5) scratches it, but a fingernail 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 | Conchoidal to uneven | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.17 | Noticeably light in the hand for its size (specific gravity about 2.17). |
Extra tests for Rock Salt
Glass check. Rock Salt shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Rock Salt look-alikes and how to tell them apart
Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Rock Salt vs Halite →
Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Rock Salt vs Anhydrite →
Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Rock Salt vs Gypsum →
Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for clear, white, pink, orange, or gray crystalline masses.
- Rock salt is soft and water-soluble.
- Cubic cleavage or blocky crystal surfaces may be visible.
- Do not taste unknown specimens; rely on safer visual and provenance clues.
Rock Salt identification FAQ
How can you tell if a rock is Rock Salt?
Check the color (clear, white, pink, and orange), the vitreous luster, a Mohs hardness of 2.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Rock Salt?
Rock Salt has a Mohs hardness of 2.5. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Rock Salt and Halite?
Rock Salt (Mohs 2.5, vitreous luster) and Halite (Mohs 2–2.5, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Rock Salt vs Halite comparison for a side-by-side table.
Is Rock Salt worth anything?
Entry-level Rock Salt specimens sell for around $1, typical collector pieces about $10, and premium examples $75 or more depending on size, quality and locality.
What color is Rock Salt?
Rock Salt is most often clear, white, pink, and orange. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
