Natrolite
Natrolite is a sodium-rich zeolite mineral that forms delicate, slender prismatic crystals, often gathered into radiating sprays. It typically occurs in cavities of basalt and is valued by collectors for its needle-like sprays.
Natrolite properties at a glance
| Type | Silicate Minerals |
|---|---|
| Chemical formula | Na2Al2Si3O10·2H2O |
| Mohs hardness | 5.5 |
| Crystal system | orthorhombic |
| Luster | vitreous |
| Streak | White |
| Cleavage | Perfect on {110} |
| Fracture | Uneven |
| Specific gravity | 2.25 |
| Transparency | transparent |
| Common colors | Colorless, White, Pink, Yellow, Gray |
| Rarity | uncommon |
Geology & background
Natrolite is a zeolite that forms when low-temperature fluids alter volcanic rocks, crystallizing in gas cavities and fractures of basalt and in some alkaline igneous rocks.
Natrolite was among the early zeolites described as scientists studied this group of water-bearing silicates, and it remains a classic mineral for understanding zeolite structures.
How to identify Natrolite
- Look for slender, needle-like white or colorless crystals, often in radiating sprays in basalt cavities.
- Natrolite is moderately soft at about 5 to 5.5 and has a low density and perfect prismatic cleavage.
- It fuses readily in a flame, helping separate it from harder silicates with similar habits.
Where Natrolite is found
Natrolite occurs in cavities of basalt and alkaline igneous rocks worldwide, with notable specimen localities in the United States, Canada, Germany, the Czech Republic, India, and Russia.
How much is Natrolite worth?
| Entry-level specimen | $8 |
|---|---|
| Typical collector specimen | $45 |
| Premium specimen | $250+ |
Value depends on crystal size, intact sprays, luster, matrix, locality, and overall aesthetic quality.
Common uses
- Collector specimens
- Mineralogical study
- Zeolite research
- Museum display
Interesting facts
- Natrolite often forms fine needle-like crystals that radiate outward like a starburst.
- Its name refers to its sodium content, from the Latin word natron for a sodium compound.
- As a zeolite it can absorb and release water, and it fuses easily before a flame.
- Some natrolite crystals are piezoelectric, generating a small charge under pressure.
Care & safety
Natrolite forms thin, brittle crystals that break easily and can lose water if strongly heated.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
Fragile needle crystals. Slender natrolite crystals snap easily; handle specimens by the matrix and avoid touching the needles.
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