Comparison · Minerals vs Silicate Minerals
Hemimorphite vs Prehnite
Hemimorphite and Prehnite are easy to confuse. Prehnite is harder (Mohs 6.25) than Hemimorphite (Mohs 4.5–5), so Prehnite will scratch Hemimorphite 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 Hemimorphite and Prehnite
- Prehnite is harder (Mohs 6.25) than Hemimorphite (Mohs 4.5–5), so Prehnite will scratch Hemimorphite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Hemimorphite feels noticeably heavier for its size (specific gravity 3.4–3.5 versus 2.88 for Prehnite).
- Hold a thin edge to the light: Hemimorphite is Transparent to translucent, Prehnite is translucent.
- They overlap in green and yellow, but Hemimorphite also comes in clear, blue, and brown and Prehnite also comes in white and gray.
- Well-formed crystals give it away: Hemimorphite is Orthorhombic, Prehnite is orthorhombic.
Hemimorphite vs Prehnite properties
| Property | Hemimorphite | Prehnite |
|---|---|---|
| Type | Minerals | Silicate Minerals |
| Mohs hardness | 4.5–5 | 6.25 |
| Luster | Vitreous, silky when fibrous | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | translucent |
| Specific gravity | 3.4–3.5 | 2.88 |
| Crystal system | Orthorhombic | orthorhombic |
| Common colors | White, Colorless, Pale blue, Green, Brown, Yellowish | Green, Yellow-green, Yellow, White, Gray |
| Rarity | common | uncommon |
| Typical specimen value | $2–$150+ | $10–$400+ |
Which is more valuable?
Prehnite is usually the more valuable of the two: a typical collector specimen runs about $70 against $20 for Hemimorphite, and premium Prehnite can reach $400 or more.
About Hemimorphite
Hemimorphite is a zinc silicate hydroxide mineral crystallizing in the orthorhombic system and named for its hemimorphic crystals, which develop different faces at opposite ends of the same crystal axis. It typically forms in the oxidized zones of zinc ore deposits, often intergrown with or resembling smithsonite, another secondary zinc mineral. Its delicate, fan-shaped crystal clusters and pastel blue to white coloring make it a favorite among collectors of secondary zinc minerals.
About Prehnite
Prehnite is a calcium aluminum silicate best known for its soft green to yellow-green color and rounded, botryoidal crystal aggregates. It commonly lines cavities in basalt and is valued by collectors and lapidaries for its translucent glow.
Hemimorphite vs Prehnite FAQ
Is Hemimorphite the same as Prehnite?
No. Hemimorphite is a mineral while Prehnite is a silicate mineral. Prehnite is harder (Mohs 6.25) than Hemimorphite (Mohs 4.5–5), so Prehnite will scratch Hemimorphite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Hemimorphite from Prehnite?
Prehnite is harder (Mohs 6.25) than Hemimorphite (Mohs 4.5–5), so Prehnite will scratch Hemimorphite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Hemimorphite feels noticeably heavier for its size (specific gravity 3.4–3.5 versus 2.88 for Prehnite). Hold a thin edge to the light: Hemimorphite is Transparent to translucent, Prehnite is translucent.
Which is harder, Hemimorphite or Prehnite?
Prehnite is harder: Mohs 6.25 against Mohs 4.5–5 for Hemimorphite.
Which is more valuable, Hemimorphite or Prehnite?
Prehnite is usually the more valuable of the two: a typical collector specimen runs about $70 against $20 for Hemimorphite, and premium Prehnite can reach $400 or more.
