Amazonite (variety of Microline - Feldspar)
Current inventory:  0 gems
 

  
Amozonite is named after the Amazon River basin in South America. The name Microline is from the Greek words mikron meaning little and klinein meaning inclined for the slight deviation of the cleavage plans from 90 degrees.

Discovered in 1830;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

KAlSi₃O₈

Potassium Aluminum Silicate

Molecular Weight:

278.33 gm

Composition:

Potassium

14.05 %

K

16.92 %

K₂O

Aluminum

9.69 %

Al

18.32 %

Al₂O₃

Silicon

30.27 %

Si

64.76 %

SiO₂

Oxygen

45.99 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.06-30

Nickel-Strunz 10th Ed. ID:

9.FA.30

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
A : Tektosilicates without additional non-tetrahedral anions

Related to:

A variety of Microline. Feldspar Group. Dimorph of Orthoclase.

Members of Group:

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

Varieties:

None

Synonyms:

Amazone Jade, Amazone Stone

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Microline crystals are prismatic and elongated, perhaps the largest of any species, to 50 m and 13,500 tons. Cleavable to granular, massive.

Twinning:

Carlsbad, Baveno, and Manebach laws very common; polysynthetic twinning on the Albite and Pericline laws give an orthogonal grid pattern.

Physical Properties

Cleavage:

Perfect on {001} and {010}, intersecting at ~90º; partings on {100}, {110}, {110}, and {201}.

Fracture:

Uneven

Tenacity:

Brittle

Moh's Hardness:

6.0 - 6.5

Density:

2.54 - 2.57 (g/cm³)

Luminescence:

Possibly Fluorescent, cherry red under SW UV

Radioactivity:

Barely Detectable; GRapi = 200.97 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Pale Green to Dark Green, Aqua Green, Bluish Green

Transparency:

Translucent to Opaque

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.514 - 1.539  Biaxial ( - )

Birefringence:

0.007

Dispersion:

Relatively weak; r > v

Pleochroism:

None

Occurances

Geological Setting:

Common in plutonic felsic rocks, as granites, granite pegmatites, syenites; in metamorphic rocks of the greenschist and amphibolite facies; in hydrothermal veins. A detrital component in sedimentary rocks and as authigenic overgrowths.

Common Associations:

Quartz, Sodic Plagioclase, Muscovite, Biotite, "Hornblende"

Common Impurities:

Fe, Ca, Na, Li, Cs, Rb, H₂O, Pb

Co-Type Localities:

Arendal, Aust-Agder, Norway
Stavern (Fredriksvärn), Larvik, Vestfold, Norway

Year Discovered:

1830

View mineral photos:

Amazonite Mineral Photos and Locations

More Information

Mindat.org (Amazonite)
Mindat.org (Microline)
Webmineral.com (Microline)

Amazonite is a member of the Potassium Feldspars of the Feldspar Group of minerals that also includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Amazonite is the green variety of Microline. Some of the most beautiful Amazonite crystals come from the Pike's Peak and Crystal Peak areas of Colorado, USA. Amazonite is almost always opaque and makes for beautifully colored cabochons. A recent find in Mogok, Myanmar (Burma) has produced a small number of extremely rare transparent crystals that have been faceted into gems. Another recent find in Vietnam has produced vivid green crystals that have been faceted into beautiful gems of amazing clarity and color.
 

  
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