Identification guide · Minerals
How to Identify Heulandite
Heulandite is commonly colorless, white, pink, peach, or brick-red, with a vitreous luster on most faces but a distinctive pearly luster on its perfect cleavage face, and it has a white streak. It has a hardness of 3.5 to 4 and one perfect cleavage direction, typically forming flattened, coffin-shaped monoclinic crystals that are a hallmark of the mineral. It is easily confused with the related zeolite stilbite, but heulandite's crystals are more tabular and blocky compared to stilbite's characteristic sheaf-like or bow-tie aggregates of thinner blades.
Heulandite identification checklist
| Color | White, Colorless, Pink, Red, Brown, Yellow | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous, pearly on cleavage | 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 | Perfect, one direction | |
| Fracture | Uneven | |
| Specific gravity | 2.1–2.2 | Noticeably light in the hand for its size (specific gravity about 2.1500000000000004). |
| Crystal system | Monoclinic |
Heulandite 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. Heulandite vs Calcite →
Apatite is harder (Mohs 5) than Heulandite (Mohs 3.5–4), so Apatite will scratch Heulandite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Heulandite vs Apatite →
Apophyllite is harder (Mohs 4.5–5) than Heulandite (Mohs 3.5–4), so Apophyllite will scratch Heulandite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Heulandite vs Apophyllite →
Both sit near Mohs 3.5–4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Heulandite identification FAQ
How can you tell if a rock is Heulandite?
Check the color (white, colorless, pink, and red), the vitreous, pearly on cleavage 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 Heulandite?
Heulandite 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 Heulandite and Calcite?
Heulandite (Mohs 3.5–4, vitreous, pearly on cleavage luster) and Calcite (Mohs 3, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Heulandite vs Calcite comparison for a side-by-side table.
Is Heulandite worth anything?
Entry-level Heulandite 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 Heulandite?
Heulandite is most often white, colorless, pink, and red. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
