Comparison · Minerals
Apophyllite vs Heulandite
Apophyllite and Heulandite are easy to confuse because both are minerals. 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. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Apophyllite and Heulandite
- 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.
- They overlap in clear, pink, and yellow, but Apophyllite also comes in green and Heulandite also comes in red and brown.
- Well-formed crystals give it away: Apophyllite is Tetragonal, Heulandite is Monoclinic.
Apophyllite vs Heulandite properties
| Property | Apophyllite | Heulandite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 4.5–5 | 3.5–4 |
| Luster | Vitreous, pearly on cleavage | Vitreous, pearly on cleavage |
| Streak | White | White |
| Transparency | Transparent to translucent | Transparent to translucent |
| Specific gravity | 2.3–2.4 | 2.1–2.2 |
| Crystal system | Tetragonal | Monoclinic |
| Common colors | Colorless, White, Green, Pink, Pale yellow | White, Colorless, Pink, Red, Brown, Yellow |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Apophyllite and Heulandite trade in a similar range, around $20.
About Apophyllite
Apophyllite is the common name for a small group of hydrated potassium calcium silicates, most often KCa4Si8O20(F,OH)·8H2O, crystallizing in the tetragonal system. It typically grows as glassy, pseudo-cubic or pyramidal crystals lining cavities in basaltic lava. The name comes from the Greek for 'to leaf away,' describing how the mineral flakes when heated, losing its water of crystallization.
About Heulandite
Heulandite is a calcium- and sodium-bearing zeolite mineral, part of a group known for its coffin-shaped monoclinic crystals with a distinctive pearly luster on one prominent cleavage face. It typically forms as a secondary mineral filling vesicles and fractures in basaltic and volcanic rocks, alongside other zeolites deposited by cooling hydrothermal fluids. Heulandite is named after English mineral collector Henry Heuland, whose collection contributed significantly to early zeolite mineralogy.
Apophyllite vs Heulandite FAQ
Is Apophyllite the same as Heulandite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. 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.
How can you tell Apophyllite from Heulandite?
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. They overlap in clear, pink, and yellow, but Apophyllite also comes in green and Heulandite also comes in red and brown. Well-formed crystals give it away: Apophyllite is Tetragonal, Heulandite is Monoclinic.
Which is harder, Apophyllite or Heulandite?
Apophyllite is harder: Mohs 4.5–5 against Mohs 3.5–4 for Heulandite.
Which is more valuable, Apophyllite or Heulandite?
Typical specimens of Apophyllite and Heulandite trade in a similar range, around $20.
