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Eucryptite
Current inventory: 0 gems
 

Eucryptite

  
Eucryptite was named in 1880 by American mineralogists George J. Brush (1831-1912) and Edward S. Dana (1849-1935) from the Greek words for well and concealed, in reference to its occurrence as intimate intergrowths with Albite.

Discovered in 1880; IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

LiAlSiO4

 

Lithium Aluminum Silicate

Molecular Weight:

126.01 gm

Composition:

Lithium

5.51 %

Li

11.86 %

Li2O

 

Aluminum

21.41 %

Al

40.46 %

Al2O3

 

Silicon

22.29 %

Si

47.68 %

SiO2

 

Oxygen

50.79 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.01-30

Nickel-Strunz 10th Ed. ID:

9.AA.05

 

9 : SILICATES (Germanates)
A : Nesosilicates
A : Nesosilicates without additional anions; cations in tetrahedral [4] coordination

Related to:

Phenakite Group.

Members of Group:

Phenakite Group: Eucryptite, Phenakite, Willemite

Varieties:

None

Synonyms:

ICSD 30982, Lithionnephelin, PDF 14-667

 

 

Crystal Data

   

   

Crystallography:

Trigonal - Rhombohedral

Crystal Habit:

Rare euhedral crystals, to 3 cm; common forms are {1010}, {1120} and {0001}. In coarse crystalline aggregates and massive.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

Poor/indistinct on {1010} and {0001}

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5

Density:

2.657 - 2.666 (g/cm3)

Luminescence:

Fluoresces pink to magenta-red or orangish-red under SW UV

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Colorless, White, Tan, Gray

Transparency:

Transparent to translucent

Luster:

Vitreous

Refractive Index:

1.570 - 1.587  Uniaxial ( + )

Birefringence:

0.0130

Dispersion:

None

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

In lithium-rich pegmatites, often as graphic intergrowths with albite derived from alteration of spodumene.

Common Associations:

Albite, Amblygonite, Lepidolite, Petalite, Quartz, Spodumene

Common Impurities:

Na, K

Type Locality:

Abija N. Fillow Quarry (Branchville Quarry), Branchville, Redding, Fairfield Co., Connecticut, USA

Year Discovered:

1880

View mineral photos:

Eucryptite Mineral Photos and Locations

 

 

Unusual Gem Categories

   

   

 

Fluorescent Gems

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Eucryptite is a rare silicate mineral and is one of very few silicate minerals that have a trigonal symmetry. It is a member of the Phenakite Group of minerals that includes
Eucryptite, Phenakite and Willemite. All three have the same basic chemical structure and symmetry, but different metal ions. Eucryptite can fluoresce a beautiful magenta red to orangish-red under shortwave (SW) ultraviolet (UV) light (put your mouse over the picture above to see the gems color under SW-UV light).

Eucryptite was named in 1880 by American mineralogists George J. Brush (1831-1912) and Edward S. Dana (1849-1935) from the Greek words for well and concealed, in reference to its occurrence as intimate intergrowths with Albite.

Eucryptite can be found in the USA, from Branchville, Fairfield County, Connecticut; Center Strafford, Strafford County, New Hampshire; in the Harding pegmatite, Dixon, Taos County, New Mexico; in the Midnight Owl pegmatite, Maricopa County, Arizona; and in the Foote mine, Kings Mountain, Cleveland County, North Carolina. From the Tanco pegmatite, Bernic Lake, Manitoba, and near Nakina, Ontario, Canada. In Zimbabwe, large amounts at Bikita, with many other minor localities. From the Haapaluoma quarry, near Peräseinäjoki, Finland.
 

  
Eucrypti
te gems for sale:

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