Prase Opal

Big Photo

Tanzania
28.87 carats
© Palagems

Prase Opal is an electric green variety of Common opal coloured by trace amounts of Nickel minerals. It is similar in colour to chrysoprase, and it can be found in the same places, but the two can be distinguished by differences in refractive index and specific gravity.

Prase Opal Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 

Prase Opal Gemstones by Size

This table shows distribution of Prase Opal gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:4.92 cts
Heaviest:28.87 cts
Average:16.90 cts
Total photos:2
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4.92ct to 7.32ct7.32ct to 9.71ct9.71ct to 12.11ct12.11ct to 14.50ct14.50ct to 16.90ct16.90ct to 19.29ct19.29ct to 21.69ct21.69ct to 24.08ct24.08ct to 26.48ct26.48ct to 28.87ct
General Information
A variety or type of:Common Opal, which is a variety of Opal
Chemical Formula
SiO
 
2
+ H
 
2
O
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Physical Properties of Prase Opal
Mohs Hardness5 to 6.5
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Specific Gravity1.98 to 2.25
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureConchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Prase Opal
Refractive Index1.370 to 1.470
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical CharacterIsotropic
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Apple-green
Walter Schumann, Gemstones of the world (2001)
More from other references
Causes of ColourGreen colour due to nickel-bearing inclusions
Lithographie, Opal (2007)
TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
LustreVitreous
Arthur Thomas, Gemstones (2009)
Crystallography of Prase Opal
Crystal SystemAmorphous
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
HabitMassive
Arthur Thomas, Gemstones (2009)
Further Information
Mineral information:Prase Opal information at mindat.org
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