Identification guide · Carbonates
How to Identify Smithsonite
Smithsonite is usually blue green, green, and blue with a vitreous luster and is translucent. It has a Mohs hardness of 4.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is white. It is most often confused with Hemimorphite, Cerussite, and Opal; the tests below separate them.
Smithsonite identification checklist
| Color | Blue green, Green, Blue, Yellow, Pink, White | 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 | 4.5 | 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 | Perfect rhombohedral | |
| Fracture | Uneven to conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 4.4 | Heavier than it looks (specific gravity about 4.4). |
| Crystal system | Trigonal |
Extra tests for Smithsonite
Acid test. Fizzes in vinegar or dilute hydrochloric acid because of its carbonate content.
Glass check. Smithsonite 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.
Smithsonite look-alikes and how to tell them apart
Both sit near Mohs 4.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Smithsonite vs Hemimorphite →
Smithsonite is harder (Mohs 4.5) than Cerussite (Mohs 3–3.5), so Smithsonite will scratch Cerussite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Smithsonite vs Cerussite →
Opal is harder (Mohs 5.5) than Smithsonite (Mohs 4.5), so Opal will scratch Smithsonite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Smithsonite vs Opal →
Labradorite is harder (Mohs 6) than Smithsonite (Mohs 4.5), so Labradorite will scratch Smithsonite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
Field tips
- Look for smooth botryoidal crusts, soft pastel colors, and a notable heft for a carbonate.
- Smithsonite has perfect rhombohedral cleavage and a hardness near four and a half.
- It can resemble hemimorphite; smithsonite is the carbonate and reacts with warm dilute acid.
Smithsonite identification FAQ
How can you tell if a rock is Smithsonite?
Check the color (blue green, green, blue, and yellow), the vitreous luster, a Mohs hardness of 4.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Smithsonite?
Smithsonite has a Mohs hardness of 4.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Smithsonite and Hemimorphite?
Smithsonite (Mohs 4.5, vitreous luster) and Hemimorphite (Mohs 4.5–5, vitreous, silky when fibrous luster) look alike, but hardness, streak and heft usually separate them. See the full Smithsonite vs Hemimorphite comparison for a side-by-side table.
Is Smithsonite worth anything?
Entry-level Smithsonite specimens sell for around $15, typical collector pieces about $120, and premium examples $900 or more depending on size, quality and locality.
What color is Smithsonite?
Smithsonite is most often blue green, green, blue, and yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
