Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10·2H2O. The type locality is Hohentwiel, Hegau, Germany.
| Natrolite | |
|---|---|
| General | |
| Category | Tectosilicate |
| Formula (repeating unit) | Na2Al2Si3O10·2H2O |
| IMA symbol | Ntr |
| Strunz classification | 9.GA.05 (10 ed) 8/J.21-10 (8 ed) |
| Dana classification | 77.01.05.01 |
| Crystal system | Orthorhombic |
| Crystal class | Pyramidal (mm2) H–M symbol: (mm2) |
| Space group | Fdd2 |
| Unit cell | a = 18.27, b = 18.587 c = 6.56 [Å], Z = 8 |
| Identification | |
| Formula mass | 380.22 g/mol |
| Color | White, colorless, sometimes pink |
| Crystal habit | Acicular |
| Twinning | On {110}, {011}, {031} |
| Cleavage | Perfect on {110} |
| Fracture | Irregular, uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 5–6 |
| Luster | Vitreous, silky, pearly |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.25 |
| References | |
It was named natrolite by Martin Heinrich Klaproth in 1803. The name is derived from natron (νατρών), the Greek word for soda, in reference to the sodium content, and lithos (λίθος), meaning stone. Needle stone or needle-zeolite are other informal names, alluding to the common acicular habit of the crystals, which are often very slender and are aggregated in divergent tufts. The crystals are frequently epitaxial overgrowths of natrolite, mesolite, and gonnardite in various orders.
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