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.

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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Photos of natural/un-cut material from mindat.org
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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