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Grandidierite
Current inventory:  1 gem
 

Grandidierite

  
Grandidierite is named after the French naturalist and explorer, Alfred Grandidier (1836-1912), an authority on the natural history and geography of Madagascar.

Discovered in 1902. IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

(Mg,Fe2+)Al3(BO3)(SiO4)O2

 

Magnesium Iron Aluminum Boro-Silicate

Molecular Weight:

296.03 gm

Composition:

Magnesium

6.16 %

Mg

10.21 %

MgO

 

Aluminum

27.34 %

Al

51.67 %

Al2O3

 

Iron

4.72 %

Fe

6.07 %

FeO

 

Silicon

9.49 %

Si

20.30 %

SiO2

 

Boron

3.65 %

B

11.76 %

B2O3

 

Oxygen

48.64 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/B.31-40

Nickel-Strunz 10th Ed. ID:

9.AJ.05

 

9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO4

Related to:

Mg analogue of Ominelite.

Varieties:

None

Synonyms:

None

 

 

Crystal Data

   

   

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

As anhedral elongated individuals, to 8 cm, typically strongly corroded.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

Perfect; more perfect on {100}, and {010}

Fracture:

Uneven

Tenacity:

Brittle

Moh's Hardness:

7.5

Density:

2.98 - 2.99 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Bluish green, Greenish blue; increasingly greener with greater Fe content.

Transparency:

Transparent, Translucent, Opaque

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.590 - 1.639  Biaxial ( - )

Birefringence:

0.0370

Dispersion:

Very strong; r < v

Pleochroism:

Visible; X = deep blue to blue-green; Y = colorless; Z = light greenish blue to deep green

 

 

Occurances

   

   

Geological Setting:

A rare accessory mineral in aluminous boron-rich rocks, thermally and high-grade regionally metamorphosed under low pressure; in pegmatites, aplites, gneisses; in xenoliths.

Common Associations:

Andalusite, Biotite, Cordierite, Corundum, Garnet, Hypersthene, Kornerupine, Plagioclase, Potassic Feldspar, Quartz, Sapphirine, Serendibite, Sillimanite, Sinhalite, Spinel, Tourmaline

Common Impurities:

Ti, Mn, Na, K

Type Locality:

Cap Andrahomana, Ranopiso Department, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar

Year Discovered:

1902

View mineral photos:

Grandidierite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Grandidierite is an extremely rare mineral and gem with a beautiful blue-green color. Although it is very rarely transparent, faceted, translucent gems have a beautiful color. The type locality, and most well known location, is Andrahomana, southwest of Fort Dauphin, southern Madagascar. Other minor sources are Kachenbere Hills, Malawi; Béjaia, Algeria; Ontario, Canada; Warren County, New York, USA; Tuscany, Italy; Maratakka, Surinam; Cuvier Island, New Zealand and Norway.
 

  
Grandidierite gems for sale:

Grandidierite-005

Gem:

Grandidierite

Stock #:

GRAND-005

Weight:

0.1960 ct

Size:

3.40 x 3.37 x 2.41 mm

Shape:

Square

Color:

Blue-green

Clarity:

Translucent

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

$470.00    [ Make offer ]

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

Grandidierite-005

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-007

Gem:

Grandidierite

Stock #:

GRAND-007

Weight:

0.0395 ct

Size:

2.72 x 1.70 x 1.13 mm

Shape:

Rectangle

Color:

Blue-green

Clarity:

VS2

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-007

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-006

Gem:

Grandidierite

Stock #:

GRAND-006

Weight:

0.0635 ct

Size:

2.57 x 1.56 mm

Shape:

Round

Color:

Blue-green

Clarity:

I2 - Translucent

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-006

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-004

Gem:

Grandidierite

Stock #:

GRAND-004

Weight:

0.2005 ct

Size:

4.37 x 3.08 x 2.25 mm

Shape:

Oval

Color:

Blue-green

Clarity:

VS2 - Translucent

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-004

A very large gem for the type with excellent color. This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-003

Gem:

Grandidierite

Stock #:

GRAND-003

Weight:

0.0660 ct

Size:

3.25 x 2.03 x 1.33 mm

Shape:

Rectangle

Color:

Blue-green & yellowish

Clarity:

VS2 - SI

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-003

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-002

Gem:

Grandidierite

Stock #:

GRAND-002

Weight:

0.0275 ct

Size:

1.83 x 1.32 mm

Shape:

Round

Color:

Blue-green

Clarity:

SI

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-002

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


Grandidierite-001

Gem:

Grandidierite

Stock #:

GRAND-001

Weight:

0.0260 ct

Size:

1.96 x 0.98 mm

Shape:

Round

Color:

Blue-green

Clarity:

VS2 - SI

Origin:

Andrahomana, Madagascar

Treatment:

None (natural)

Price:

SOLD (but we have others)

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

Grandidierite-001

This extemely rare gem is from Madagascar. Grandidierite is considered to be one of the ten rarest gemstones in the world according to curiousnotions.com.


 


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