Identification guide · Minerals
How to Identify Datolite
Datolite typically appears colorless, pale green, yellow, or pink, with a vitreous, glassy luster on well-formed crystal faces, though massive nodular material can look dull and porcelain-like. Its streak is white, hardness is about 5 to 5.5, and it lacks a well-developed cleavage, breaking instead with a conchoidal fracture typical of glassy minerals. Crystal habit ranges from short, stubby prisms to dense, rounded nodules. It is sometimes confused with prehnite or zeolite minerals found in similar basalt cavities, but datolite's greater hardness and glassier luster set it apart.
Datolite identification checklist
| Color | Colorless, White, Pale green, Yellow, Pink | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous, slightly greasy | 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 | 5–5.5 | 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 | Poor/indistinct | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.9–3.0 | Ordinary rock-like heft (specific gravity about 2.95), similar to quartz. |
| Crystal system | Monoclinic |
Extra tests for Datolite
Glass check. Datolite 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.
Datolite look-alikes and how to tell them apart
Feldspar is harder (Mohs 6–6.5) than Datolite (Mohs 5–5.5), so Feldspar will scratch Datolite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Datolite vs Feldspar →
Datolite is harder (Mohs 5–5.5) than Calcite (Mohs 3), so Datolite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Datolite vs Calcite →
Both sit near Mohs 5–5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Datolite vs Analcime →
Both sit near Mohs 5–5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Datolite identification FAQ
How can you tell if a rock is Datolite?
Check the color (colorless, white, pale green, and yellow), the vitreous, slightly greasy luster, a Mohs hardness of 5–5.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Datolite?
Datolite has a Mohs hardness of 5–5.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Datolite and Feldspar?
Datolite (Mohs 5–5.5, vitreous, slightly greasy luster) and Feldspar (Mohs 6–6.5, vitreous to pearly luster) look alike, but hardness, streak and heft usually separate them. See the full Datolite vs Feldspar comparison for a side-by-side table.
Is Datolite worth anything?
Entry-level Datolite 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 Datolite?
Datolite is most often colorless, white, pale green, and yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
