Identification guide · Sedimentary Rocks
How to Identify Caliche
Caliche is usually white, cream, and tan with a dull luster and is opaque. It has a Mohs hardness of 3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Its streak is white to pale tan. It is most often confused with Limestone, Dolostone, and Diatomite; the tests below separate them.
Caliche identification checklist
| Color | White, Cream, Tan, Gray, Brown | 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 | 3 | A copper coin (Mohs 3.5) scratches it, but a fingernail does not. |
| Streak | White to pale tan | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Variable by mineral grains | |
| Fracture | Earthy to uneven | |
| Specific gravity | 2.4 | Ordinary rock-like heft (specific gravity about 2.4), similar to quartz. |
Extra tests for Caliche
Acid test. Fizzes in vinegar or dilute hydrochloric acid because of its carbonate content.
Caliche look-alikes and how to tell them apart
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Caliche vs Limestone →
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Caliche vs Dolostone →
Caliche is harder (Mohs 3) than Diatomite (Mohs 1.5), so Caliche will scratch Diatomite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Caliche vs Diatomite →
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for hard, pale, earthy carbonate cement in soil-like or near-surface material.
- Caliche is common in dry-region soils and may occur as nodules, crusts, or ledges.
- It may fizz with dilute acid because it contains calcium carbonate.
- Texture can include cemented sand, gravel, clay, or root-like structures.
Caliche identification FAQ
How can you tell if a rock is Caliche?
Check the color (white, cream, tan, and gray), the dull luster, a Mohs hardness of 3 and a white to pale tan streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Caliche?
Caliche has a Mohs hardness of 3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Caliche and Limestone?
Caliche (Mohs 3, dull luster) and Limestone (Mohs 3, dull luster) look alike, but hardness, streak and heft usually separate them. See the full Caliche vs Limestone comparison for a side-by-side table.
Is Caliche worth anything?
Entry-level Caliche 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 Caliche?
Caliche is most often white, cream, tan, and gray. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
