Click on a letter above to view the list of gems.    

  

 


Bertrandite
Current inventory:  0 gems
 

Bertrandite

  
Bertrandite is named in honor of French mineralogist Emile Bertrand (1844 - 1909).

Discovered in 1883;   IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

Be4(Si2O7)(OH)2

 

Beryllium Silicate Hydroxide

Molecular Weight:

238.23 gm

Composition:

Beryllium

15.13 %

Be

42.00 %

BeO

 

Silicon

23.58 %

Si

50.44 %

SiO2

 

Hydrogen

0.85 %

H

7.56 %

H2O

 

Oxygen

60.44 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/C.07-10

Nickel-Strunz 10th Ed. ID:

9.BD.05

 

9 : SILICATES (Germanates)
B : Sorosilicates
D : Si
2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination

Related to:

Bertrandite-Strontiochevkinite Series.

Varieties:

Gel-Bertrandite

Synonyms:

Hessenbergite

 

 

Crystal Data

   

   

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Crystals thin tabular, commonly prismatic to needlelike, to 5 cm; in radial aggregates.

Twinning:

Common on [011] or [021]; twins heart-shaped or V-shaped with axes crossing at angles of about 60 and 120.

 

 

Physical Properties

   

 

Cleavage:

Perfect on {001}; Distinct on {100}, {010}, and {110}

Fracture:

n/a

Tenacity:

Brittle

Moh's Hardness:

6.0 - 7.0

Density:

2.59 - 2.60 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Pyroelectric

 

 

Optical Properties

   

   

Color:

Colorless, pale Yellow

Transparency:

Translucent to Transparent

Luster:

Vitreous, Pearly on cleavage {001}

Refractive Index:

1.583 - 1.614  Biaxial ( - )

Birefringence:

0.0230

Dispersion:

Weak; r < v

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

In fissures in granites and associated pegmatites and in miarolitic cavities in greisens; commonly an alteration product of beryl, more rarely as a primary mineral.

Common Associations:

Beryl, Fluorite, Herderite, Muscovite, Phenakite, Quartz, Tourmaline.

Common Impurities:

Al, Fe, Ca

Co-Type Localities:

Barbin Quarry, Nantes, Loire-Atlantique, Pays de Loire, France;
Petit-Port, Nantes, Loire-Atlantique, Pays de Loire, France

Year Discovered:

1883

View mineral photos:

Bertrandite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Bertrandite is a fairly common mineral but rarely faceted since crystals are rarely large enough or clean enough for faceting. It is an important ore of beryllium second only to Beryl. Bertrandite and Beryl are often found associated together. Bertrandite is an alteration product of Beryl and it is not unusual to find occurances of Bertrandite completely replacing Beryl crystals forming a psuedomorph. A psuedomorph is when one mineral replaces another on an atom by atom basis, replacing the chemistry and structure with the new mineral but preserving the external shape of the original crystal. Bertrandite gems are usually very small, colorless and included.

Bertrandite is found in small amounts at numerous localities but gem quality crystals are rare. A few locations include Golconda mine, near Governador Valadares, Minas Gerais, Brazil; Barbin quarries at Petit-Port, Loire-Atlantique, France; Akchatau, Kara-Oba, and Kounrad, Kazakhstan; and in the USA on Mt. Antero, Chaffee County, Colorado; at the Strickland quarry, Portland, Middlesex County, Connecticut.
 

  
Bertrandi
te gems for sale:

We have not photographed our Bertrandite gems yet. Please check back soon.
 

 


I love Sarah