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Andesine

 

Andesine (variety of Albite, Feldspar)

 

Discovered in 1841;   IMA status: Not Valid (a variety of Albite, Feldspar)

 

Chemistry

 

 

Chemical Formula:

(Na,Ca)[Al(Si,Al)Si2O8]

 

Sodium Calcium Aluminum Silicate

Molecular Weight:

521.21 gm

Composition:

Sodium

5.14 %

Na

6.92 %

Na2O

 

Calcium

5.97 %

Ca

8.35 %

CaO

 

Aluminum

14.06 %

Al

26.57 %

Al2O3

 

Silicon

27.18 %

Si

58.16 %

SiO2

 

Oxygen

47.65 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.07-40

Nickel-Strunz 10th Ed. ID:

9.FA.35

 

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H
2O
A : Tektosilicates without additional non-tetrahedral anions

Related to:

Feldspar Group. Plagioclase Series. Low- and high-temperature structural modifications are recognized.

Members of Group:

Feldspar Group: Albite, Andesine, Anorthoclase, Banalsite, Buddingtonite, Bytownite, Celsian, Dmisteinbergite, Hyalophane, Labradorite, Microline, Oligoclase, Orthoclase, Paracelsian, Reedmergnerite, Sanidine, Slawsonite, Stronalsite, Svyatoslavite

Varieties:

None

Synonyms:

Andesite (of Dana)

 

 

Crystal Data

   

   

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals rare, to 2 cm; commonly massive, cleavable, or granular.

Twinning:

Commonly twinned after Albite, Pericline, and Carlsbad laws. Also twinned after a law similar to the Manebach law.

 

 

Physical Properties

   

 

Cleavage:

Perfect on {001}, less Perfect on {010}, {110} observed

Fracture:

Irregular/Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0 - 6.5

Density:

2.66 - 2.68 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

White, Grayish, Green, Yellow, Reddish, Orangish-Red, Red

Transparency:

Transparent to Translucent

Luster:

Subvitreous to Pearly

Refractive Index:

1.543 - 1.562  Biaxial ( +/- )

Birefringence:

0.0080 - 0.0090

Dispersion:

Weak, r > v

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

Widespread in igneous rocks of intermediate silica content, as syenites and andesites. Characteristic of granulite to amphibolite facies metamorphism, commonly as antiperthite; as detrital grains in sedimentary rocks.

Common Associations:

Quartz, Potassic Feldspar, Biotite, Hornblende, Magnetite

Common Impurities:

None

Type Locality:

Marmato Mine, Marmato, Cauca, Chocó Department, Colombia

Year Discovered:

1841

View mineral photos:

Andesine Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 

Andesine is a variety of Albite and a member of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Andesine is an intermediate member of the Plagioclase Feldspars in a solid solution series between Albite and Anorthite and close to Labradorite. It is a common rock building mineral but crystals are rare.

Andesine was named in 1841 by Otto Wilhelm Herman von Abich (1806–1886) for the Andes Mountains of South America where it is abundant in the lavas.

Sources of gem quality Andesine crystals are from recent finds in Congo, China and Tibet. A small find in 2002 in the Goma area of the Democratic Republic of Congo produced a relatively small quantity of beautiful red, green and yellow gems. The China Andesine is not as intense red as the Congo material, more of an orangish-red. Another find of gem quality crystals occurred in Tibet in 2005. This material, also called Tibet Sunstone, is more of a yellow to greenish-yellow base color with weak to strong coppery overtones. The Tibet Andesine has very different look from the intense red of the Congo Andesine, but still makes very beautiful and unique gems.

Andesine gems for sale:

Andesine-001

Gem:

Andesine (Feldspar)

Stock #:

ANDES-001

Weight:

0.4930 ct

Size:

5.47 x 3.54 mm

Shape:

Round

Color:

Red

Clarity:

Loupe clean

Origin:

Unknown

Treatment:

Unknown

Price:

$64.00

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

Andesine-001

A rare and beautiful, very well cut, very bright red gem from the Democratic Republic of Congo.


Andesine-002

Gem:

Andesine (Feldspar)

Stock #:

ANDES-002

Weight:

0.6295 ct

Size:

6.06 x 5.96 x 3.77 mm

Shape:

Trillion

Color:

Orangish-Red

Clarity:

Eye clean

Origin:

Unknown

Treatment:

Unknown

Price:

$70.00

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

Andesine-002

A rare and beautiful, very bright orangish-red, very well cut gem from China.

 


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