Identification guide · Minerals
How to Identify Aragonite
Aragonite shows a vitreous to slightly resinous luster, a white streak, and colors ranging from colorless and white to pale yellow, blue, or green depending on trace impurities. Its hardness of 3.5 to 4 is close to calcite's, but its crystal habit differs: aragonite favors elongated prisms, needle-like sprays, or pseudohexagonal twins rather than calcite's classic rhombohedra. Like calcite, it effervesces readily in dilute hydrochloric acid, so acid testing alone cannot separate the two minerals; crystal shape and slightly higher density are the more reliable clues.
Aragonite identification checklist
| Color | Colorless, White, Yellow, Gray, Blue, Pink | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to resinous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Transparent to translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 3.5–4 | 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 | Distinct, two directions (pseudo-hexagonal) | |
| Fracture | Subconchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.93–2.95 | Ordinary rock-like heft (specific gravity about 2.9400000000000004), similar to quartz. |
| Crystal system | Orthorhombic |
Extra tests for Aragonite
Acid test. Fizzes in vinegar or dilute hydrochloric acid because of its carbonate content.
Glass check. Aragonite 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.
Aragonite look-alikes and how to tell them apart
Both sit near Mohs 3.5–4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Aragonite vs Calcite →
Analcime is harder (Mohs 5–5.5) than Aragonite (Mohs 3.5–4), so Analcime will scratch Aragonite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Aragonite vs Analcime →
Both sit near Mohs 3.5–4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Aragonite vs Anhydrite →
Apatite is harder (Mohs 5) than Aragonite (Mohs 3.5–4), so Apatite will scratch Aragonite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
Aragonite identification FAQ
How can you tell if a rock is Aragonite?
Check the color (colorless, white, yellow, and gray), the vitreous to resinous luster, a Mohs hardness of 3.5–4 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Aragonite?
Aragonite has a Mohs hardness of 3.5–4. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Aragonite and Calcite?
Aragonite (Mohs 3.5–4, vitreous to resinous luster) and Calcite (Mohs 3, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Aragonite vs Calcite comparison for a side-by-side table.
Is Aragonite worth anything?
Entry-level Aragonite specimens sell for around $2, typical collector pieces about $20, and premium examples $150 or more depending on size, quality and locality.
What color is Aragonite?
Aragonite is most often colorless, white, yellow, and gray. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
