Natrolite

Discovered in 1803; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Na₂Al₂Si₃O₁₀ • 2H₂O

Hydrated Sodium Aluminum Silicate

Molecular Weight:

380.22 gm

Composition:

Sodium

12.09 %

Na

16.30 %

Na₂O

Aluminum

14.19 %

Al

26.82 %

Al₂O₃

Silicon

22.16 %

Si

47.41 %

SiO₂

Hydrogen

1.06 %

H

9.48 %

H₂O

Oxygen

50.49 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.21-10

Nickel-Strunz 10th Ed. ID:

9.GA.05

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H₂O; zeolite family
A : Zeolites with T₅O₁₀ Units – The Fibrous Zeolites

Related to:

Zeolite Group. Natrolite Subgroup. Dimoroh of Gonnardite.

Members of Group:

Zeolite Group: Amicite, Barrerite, Bellbergite, Bikitaite, Boggsite, Brewsterite, Chabazite, Chabazite-Lévyne Subgroup, Clinoptilolite, Cowlesite, Dachiardite-Na, Epistilbite, Erionite, Faujasite Subgroup, Ferrierite, Garronite, Gismondine, Gmelinite, Gobbinsite, Goosecreekite, Harmotome, Heulandite, Laumontite, Lévyne, Mazzite, Merlinoite, Montesommaite, Mordenite, Offretite, Paulingite, Pollucite, Stellerite, Stilbite, Thomsonite, Tschernichite, Wairakite, Willhendersonite, Yugawaralite

Members of Subgroup:

Natrolite Subgroup: Gonnardite, Mesolite, Natrolite, Paranatrolite, Scolecite

Varieties:

Bergmannite, Galactite, Germanate-natrolite, Kondrikovite, Mooraboolite, Spreustein

Synonyms:

Ædelite (of Kirwan), Aedelite, Apoanalcite, Bergmannite, Crocalite, Crockalite, Epinatrolite, Fargite, Feather Zeolite, Galactite, Lehuntite, Mealy Zeolite, Mesotype, Natronite (of ?), Needlestone, Portite

Crystal Data

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Crystals short to long prismatic, to 1 m, striated. In stellate or interlacing groups; also radiating fibrous, granular, or compact, massive.

Twinning:

On {110}, {011}, {031}

Physical Properties

Cleavage:

Perfect on {110}, parting on {010}

Fracture:

Irregular/uneven

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0; Vickers: VHN200=1239 - 1467 kg/mm²

Density:

2.20 - 2.26 (g/cm³)

Luminescence:

Fluorescent; SW UV = yellow-orange, pale green, LW UV = yellow-orange, greenish white

Radioactivity:

Not Radioactive

Other:

Piezoelectric and Pyroelectric

Optical Properties

Color:

Colorless, white, gray, bluish, pink, yellowish white

Transparency:

Transparent to translucent

Luster:

Vitreous to pearly, silky

Refractive Index:

1.473 - 1.496  Biaxial ( + )

Birefringence:

0.0120 - 0.0130

Dispersion:

Weak, r < v (0.005)

Pleochroism:

Weak; X = colorless, Y = colorless, Z = colorless

Occurances

Geological Setting:

In cavities in amygdaloidal basalts and related igneous rocks, one of the last minerals to form; fills seams in granite, gneiss, and syenite.

Common Associations:

Zeolites, Calcite, Nepheline, Sodalite, Quartz

Common Impurities:

Ca, K

Type Locality:

Hohentwiel, Singen, Hegau, Baden-Württemberg, Germany 

Year Discovered:

1803

View mineral photos:

Natrolite Mineral Photos and Locations

Unusual Gem Categories

Fluorescent Gems, Piezoelectric Gems, Pyroelectric Gems

More Information

Mindat.org
Webmineral.com

Natrolite is one of the more popular and well known members of the Zeolite Group of minerals that includes over 40 minerals and these gem-type minerals: Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite-Na, Goosecreekite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite and Yugawaralite. Natrolite usually forms as elongated crystals so faceted gems are often cut as elongated emerald cut gems. Natrolite gems are colorless and have weak dispersion and might be considered somewhat uninteresting except for the fact that Natrolite is both piezoelectric and pyroelectric and commonly exhibits yellow to orange or pale green fluorescence under both shortwave and longwave UV light.

Natrolite was discovered in 1803 at Hohentwiel, Singen, Hegau, Baden-Württemberg, Germany. Hohentwiel is an extinct volcano. Natrolite was named by German chemist Martin Heinrich Klaproth (1743-1817) from the Latin word natron meaning soda, for its sodium content, and the Greek word λίθος, (lithos) meaning stone.

Crystals can be found in many locations worldwide but gem quality crystals are relatively rare. Notable occurances are the Höwenegg quarry, Hegau, Baden-Württemberg, Germany (the Type Locality); Puy de Marman, near Veyre, Puy-de-Dôme, France. In the Dean quarry, St. Keverne, Lizard Peninsula, Cornwall, England; White Head, County Antrim, Ireland; Langesundsfjord and Tvedalen areas, Norway; Khibiny and Lovozero massifs, Kola Peninsula, Russia (large crystals); in the USA, at Bound Brook, Somerset County, New Jersey; from north of Livingstone, Park County, Montana; around Springfield, Lane County, Oregon; and at the Gem mine, San Benito County, California, USA. In Canada, huge crystals from the Johnston asbestos mine, near Thetford, and from Mont Saint-Hilaire, Quebec; in the Bay of Fundy district, Nova Scotia; and along the Ice River, British Columbia.

  
Natrolite gems for sale: