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Sellaite
Current inventory:  1 gem
 

Sellaite

Chemistry:  MgF2

Discovered in 1868;   IMA status: Valid (pre-IMA; Grandfathered).
Sellaite is named after the Italian mining engineer and minerologist Quintino Sella (1827-1884).

 

Classification

   

   

Mineral Classification:

Halides

Strunz 8th Ed. ID:

3/A.06-10

Nickel-Strunz 10th Ed. ID:

3.AB.15

 

3 : HALIDES
A : Simple halides, without H
2O
B : M:X = 1:2

Related to:

Sellaite Series

 

 

Crystal Data

   

   

Crystallography:

Tetragonal - Ditetragonal Dipyramidal

Crystal Habit:

Crystals are stout prismatic to acicular. Also fibrous aggregates.

Twinning:

On [011]

 

 

Physical Properties

   

 

Cleavage:

[100] Distinct, [110] Distinct

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 5.5

Density:

3.14 - 3.15 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Very slightly soluble in water.

 

 

Optical Properties

   

   

Color:

Colorless, White

Transparency:

Transparent

Luster:

Vitreous

Refractive Index:

1.378 - 1.390  Uniaxial ( + )

Birefringence:

0.0120

Dispersion:

0.014 (low)

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

In bituminous dolomite-anhydrite rock in a glacial moraine.

Common Associations:

Anhydrite, Gypsum, Sulphur

Type Locality:

Gébroulaz glacier, Val Thorens, Savoie, Rhône-Alpes, France

Year Discovered:

1868

View mineral photos:

Sellaite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Sellaite is an exceedingly rare gem. Crystals from Brazil are the only current facetable material. Crystals are very small with very little transparent area for faceting. Sellaite is a Halide mineral along with Boleite, Fluorite and
Villiaumite.

Sellaite is an interesting mineral in that it forms in a wide variety of geologic environments. It forms in a bituminous dolomite-anhydrite rock (Gebroulaz glacier, France); in evaporites (Bleicherode, Germany); in volcanic ejecta and fumarolic deposits (Vesuvius, Italy); in marble (Carrara, Italy); in a metamorphic magnesite deposit (Brumado mine, Brazil); and in an alkalic granite (Lake Gjerdingen, Norway).
 

  
Sellaite gems for sale:

Sellaite-001A

Gem:

Sellaite

Stock #:

SELLA-001

Weight:

0.1765 ct

Size:

4.90 x 2.49 x 1.52 mm

Shape:

Cut-corner rectangle

Color:

Colorless

Clarity:

VSI

Origin:

Brumado, Bahia, Brazil

Treatment:

None (natural)

Price:

$353.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Sellaite-001B

This small gem is considered fairly large and clean for the type. It is an extremely rare Halide gem.

 

 

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