Actinolite

Big Photo

Brazil
0.16 carats
© Rarestone.com

Actinolite is named after Greek word "aktis" - a ray, alluding to its common occurence as radiating needles.

Chatoyant, translucent to opaque, green to yellowish green colour stones are cut into cabochons and called Actinolite cat's eye. Transparent well-developed crystals of actinolite are rare and are faceted into small attractive gems for collectors.
3 photos

Actinolite Gemstones by Colour

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

Actinolite Gemstones by Size

This table shows distribution of Actinolite 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:0.16 cts
Heaviest:1.79 cts
Average:1.14 cts
Total photos:3
Do you have a larger Actinolite? Why not upload a photo?
0.16ct to 0.32ct0.32ct to 0.49ct0.49ct to 0.65ct0.65ct to 0.81ct0.81ct to 0.98ct0.98ct to 1.14ct1.14ct to 1.30ct1.30ct to 1.46ct1.46ct to 1.63ct1.63ct to 1.79ct
General Information
Varieties/Types:
Smaragdite - An emerald-green actinolite.
Chemical Formula
Ca
 
2
(Mg,Fe)
 
5
Si
 
8
O
 
22
(OH)
 
2
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Physical Properties of Actinolite
Mohs Hardness5.5 to 6
Walter Schumann, Gemstones of the world (2001)
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Specific Gravity3.03 to 3.07
Walter Schumann, Gemstones of the world (2001)
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TenacityBrittle
Anthony et al, Handbook of Mineralogy (2001) Tough in fibrous aggregates
Cleavage QualityPerfect
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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FractureUneven
Arthur Thomas, Gemstones (2009)
Optical Properties of Actinolite
Refractive Index1.6 to 1.63
Gemmologie (2000) Zeitschrift der Deutschen Gemmologischen Gesellschaf
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Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.03
Gemmologie (2000) Zeitschrift der Deutschen Gemmologischen Gesellschaf
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PleochroismDistinct: yellow-green - light green - blue-green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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DispersionNil
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Green, brown, gray, white and colourless.
Walter Schumann, Gemstones of the world (2001)
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Causes of ColourYellowish green to green (nephrite), Fe2+ in octahedral coordination
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous
Arthur Thomas, Gemstones (2009)
Crystallography of Actinolite
Crystal SystemMonoclinic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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HabitLong bladed crystals
Arthur Thomas, Gemstones (2009)
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Geological Environment
Where found:Produced by low-grade regional or contact metamorphism of magnesium carbonate, mafic, or ultramafic rocks; also in glaucophane bearing blueschists.
Anthony et al, Handbook of Mineralogy (2001)
Further Information
Mineral information:Actinolite information at mindat.org
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