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Gmelinite-Na
Current inventory:  0 gems
 

Chemistry:  (Na₂;Ca)Al₂Si₄O₁₂ ²6H₂O  
[Hydrated Sodium Calcium Aluminum Silicate]

Discovered in 1825;   IMA status: Valid (pre-IMA; Grandfathered).
Gmelinite-Na is named after the German mineralogist and chemist, Christian Gottlob Gmelin (1792-1860) of Tübingen, Germany and its Sodium (Na) content.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.26-50

Nickel-Strunz 10th Ed. ID:

9.GD.05

9.GD.05

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H₂O; zeolite family
D : Chains of 6-membered rings – tabular zeolites

Related to:

Zeolite Group. Willhendersonite - Chabazite - Perialite Series. The sodium-dominant member of the Gmelinite Series.

Crystal Data

Crystallography:

Hexagonal - Dihexagonal Dipyramidal

Crystal Habit:

As euhedral crystals, pyramidal, tabular, or rhombohedral, striated || (0001) or less commonly, || [0001], to 4 cm. Rarely in radiating aggregates or granular.

Twinning:

Penetration twins on {1011}, common.

Physical Properties

Cleavage:

[1010] Distinct

Fracture:

Vitreous

Tenacity:

Brittle

Hardness (Mohs):

4.5

Density:

2.02 - 2.17 (g/cm³)

Luminescence:

None

Radioactivity:

Barely Detectable; GRapi = 4.58 (Gamma Ray American Petroleum Institute Units) 

Other:

Piezoelictric

Optical Properties

Color:

Colorless, White, Reddish White, Salmon-Red, Yellowish, Greenish White; Colorless in thin section

Transparency:

Transparent to Translucent, Opaque

Luster:

Vitreous

Refractive Index:

1.474 - 1.494  Uniaxial ( +/- ); may be anomalously Biaxial

Birefringence:

0.0020 - 0.0130

Dispersion:

Strong

Pleochroism:

None

Occurances

Geological Setting:

Formed from sodium-rich fluids, in basalts and related igneous rocks, also pegmatites.

Common Associations:

Aragonite, Calcite, Quartz, Zeolites

Type Locality:

Nero Mt., San Pietro, Montecchio Maggiore, Vicenza Province, Veneto, Italy

Year Discovered:

1825

View mineral photos:

Gmelinite-Na Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Gmelinite-Na is one of the rarest 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. Most of these minerals are typically found only as very fine, radiating needles, cottony aggregates or radiating masses so gem quality crystals are somewhat rare. Gmelinite crystals however, are hexagonal in outline and dipyramid (two identical pyramids at the top and bottom).

Widespread in small amounts. A few localities for well studied material follow. From Montecchio Maggiore, Vicenza, Italy. At Glenarm and elsewhere in County, Antrim, Ireland. On the Isle of Skye, Scotland. At Pyrgos, Cyprus. On Pinnacle Rock, Five Islands, and Two Islands, Nova Scotia, Canada. In the Il¶³maussaq intrusion, southern Greenland. At Sarbay-Sokolov, Kazakhstan. Large crystals from Bekiady, Madagascar. From around Flinders, Victoria, Australia. In the USA, from Bergen Hill, Hudson County, and Great Notch, Paterson, and Prospect Park, Passaic County, New Jersey; at Springfield, Lane County, Oregon.
 

  
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