HomeGemsBaseOther Popular GemsPrasiolite ('Green Amethyst')
Introduction and History

Prasiolite is produced by heating violet amethyst or yellowish quartz from the deposit Montezuma in Minas Gerais, Brazil to a temperature of about 500 degrees C. The colour change is permanent, the green colour will not fade.

 

Here are a couple of informative links about greened amethyst:
http://www.gaaj-zenhokyo.co.jp/researchroom/kanbetu/2006/2006_05-01en.html
http://www.quartzpage.de/prasiolite.html

Immerse green quartz in water and viewing through crossed polaroids to look for Brazil twinning. Although synthetic amethyst has been made which exhibits Brazil twinning, there is no evidence that this material is available commercially. Green quartz is most commonly produced by the heat treatment of certain varieties of amethyst. It has also been reported to occur naturally at the California/Nevada border, although this has been disputed.
There is currently no way to determine the difference between naturally occurring green quartz and the "greened" amethyst that has been heat treated.
In the Winter 06 Gems & Gemology
The Montezuma mine in the Rio Pardo region of Minas Gerais became famous in
the '60's for the a special amethyst that could be heated and "greened".
They are now mining there again because they have discovered this amethyst
variety could be treated with a combination of heat and irradiation and
produce an unusual violetish blue color.
Heat reduces the oxidation state of iron in amethyst. At 300-500 degrees
Celcius, the color changes from purple to colorless, yellow or green. Green
quartz that is produced in this way is quite stable, whereas, green quartz
produced via gamma irradiation to colorless quartz, is not stable in
sunlight or when heated to approximately 150-200 degrees Celcius.
Seperating heat treated vs. irradiated green quartz can be done with a
Chelsea filter in incandescent light.


Heated: appears green with the filter
Irradiated: appears red

Chemistry and Crystallography
Chemical Composition  
Crystallographic System  
Cleavage  
Fracture  
Fracture Lustre  
Habit  



Physical Characteristics

Hardness  
Toughness  
Specific Gravity  
Streak  



Optical Characteristics

Colour and Cause  
Degree of Transparency  
Polish Lustre  
Refractive Index  
Birefringence  
Optic Character  
Pleochroism  
Dispersion  
Phenomena  
X-Ray Fluorescence  
Transparency to X-Rays  
Ultraviolet Fluorescence  
Chelsea Filter Reaction  
Absorption Spectra  



Description

Appearance  
Variety and Trade Names  
Misnomers  
Typical Size Range  
Typical Cutting Styles  

 

Inclusions 

Treatments 

Synthetics 

Origin 

Locality 

Care

 

Cleaning Methods ultrasonic:
steamer:
warm soapy water:
Stability reaction to heat:
stability to light:
reaction to chemicals:


Market 

Availability  
Public Recognition  
Wearability  
Recommended Disclosures  
Value  

Key Separations, Suggestions for Testing and Evaluation

 

Possibilities for Confusion

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The Geohavens name is an assurance of timeless beauty, distinct quality and uncompromising value. The Company spares no effort in sourcing from the farthest markets and the deepest mines in order to unearth the most attractive gems.

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