Identification guide · Silicate Minerals
How to Identify Stilbite
Stilbite is usually white, pink, and salmon with a vitreous luster and is transparent. It has a Mohs hardness of 3.75. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is white. It is most often confused with Heulandite, Calcite, and Apophyllite; the tests below separate them.
Stilbite identification checklist
| Color | White, Pink, Salmon, Yellow, Brown | 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 | Transparent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 3.75 | 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 in one direction | |
| Fracture | Uneven | |
| Specific gravity | 2.2 | Noticeably light in the hand for its size (specific gravity about 2.2). |
| Crystal system | Monoclinic |
Stilbite look-alikes and how to tell them apart
Both sit near Mohs 3.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Stilbite vs Heulandite →
Both sit near Mohs 3.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Stilbite vs Calcite →
Apophyllite is harder (Mohs 4.5–5) than Stilbite (Mohs 3.75), so Apophyllite will scratch Stilbite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Stilbite vs Apophyllite →
Quartz is harder (Mohs 7) than Stilbite (Mohs 3.75), so Quartz will scratch Stilbite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
Field tips
- Look for sheaf-like or bowtie-shaped crystal bundles with a pearly luster on cleavage surfaces.
- Low hardness near 3.5 to 4, low density, and occurrence in basalt cavities are strong clues.
- White to salmon-pink color with other zeolites such as apophyllite supports the identification.
Stilbite identification FAQ
How can you tell if a rock is Stilbite?
Check the color (white, pink, salmon, and yellow), the vitreous luster, a Mohs hardness of 3.75 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Stilbite?
Stilbite has a Mohs hardness of 3.75. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Stilbite and Heulandite?
Stilbite (Mohs 3.75, vitreous luster) and Heulandite (Mohs 3.5–4, vitreous, pearly on cleavage luster) look alike, but hardness, streak and heft usually separate them. See the full Stilbite vs Heulandite comparison for a side-by-side table.
Is Stilbite worth anything?
Entry-level Stilbite specimens sell for around $5, typical collector pieces about $40, and premium examples $250 or more depending on size, quality and locality.
What color is Stilbite?
Stilbite is most often white, pink, salmon, and yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
