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Actinolite

Amphibole

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)
Published: June 2014
Modified: November 2021
Actinolite Polished Actinolite Rough
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Table of Contents
  • General Information
  • Actinolite Colors
  • Alternate Names
  • Countries of Origin
  • Care
  • More About Actinolite
  • Species/Variety
  • Optical Phenomena

Actinolite is often found as needle like inclusions within other stones. It often occurs as green blades in quartz from Brazil. Byssolite, the fibrous variety of actinolite, is one of the two minerals responsible for horsetail inclusions in demantoid garnet. Popular with collectors, this generally transparent to translucent stone is often seen as individual crystals or compact fibrous masses. Actinolite gets its name from the Greek word aktinos which means “ray” or “beam.” It's also sometimes called ray stone. Actinolite is generally transparent or translucent green, green-black, or gray green in color. Actinolite is a 5.5 - 6 on the Mohs scale of hardness. It cleaves easily and is difficult to facet.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Actinolite
Species
Amphibole
Transparency
Transparent - Opaque
Dispersion
Strength: None
Refractive Index
1.614-1.641
Tolerance:(+0.014/-0.014)
Birefringence
0.022-0.027
Optic Character
Biaxial
Optic Sign
Negative
Polariscope Reaction
Aggregate (AGG), Doubly Refractive (DR)
Fluorescence
SWUV: Inert
LWUV: Inert
Pleochroism
Dichroic, moderate yellow and dark green.
Hardness
5-6
Streak
White
Specific Gravity
2.950-3.100 Typical:3.000
Toughness
Varies
Inclusions
It is the fibrous structure that causes chatoyancy.
Luster
Vitreous
Stability
Good
Fracture
Even
Cleavage
Perfect, in two directions
Chemical Name
calcium magnesium iron silicate hydroxide
Chemical Formula
Ca2(Mg, Fe)5Si8O22(OH)2
Crystal System
Monoclinic
Chemistry Classification
Silicate

Actinolite Colors

  • Black Actinolite
    Black
  • Brown Actinolite
    Brown
  • Gray Actinolite
    Gray
  • Green Actinolite
    Green
  • White Actinolite
    White

Alternate Names

Smaragdite

Countries of Origin

Papua New Guinea; Sudan; Kazakhstan; Portugal; Solomon Islands; Greece; Mongolia; Morocco; Unknown; Mali; Guatemala; Guyana; Iraq; Chile; Nepal; Argentina; Ukraine; Zambia; India; Canada; Turkey; Belgium; Namibia; Finland; South Africa; Georgia; Jamaica; Peru; Venezuela (Bolivarian Republic of); Germany; Yemen; Tanzania, United Republic Of; Eritrea; Fiji; Hong Kong; Chad; Madagascar; Thailand; United Kingdom of Great Britain and Northern Ireland; Costa Rica; Sweden; Poland; Bulgaria; Croatia; Syrian Arab Republic; Sri Lanka; Kenya; Switzerland; Spain; Azerbaijan; Cuba; Liberia; Burkina Faso; Mauritania; Guernsey; Congo (the Democratic Republic of the); Australia; Myanmar; Cameroon; Malaysia; Iceland; Oman; Armenia; Gabon; Austria; El Salvador; Korea (the Republic of); Brazil; Algeria; Slovenia; Colombia; Ecuador; Hungary; Republic of Kosovo; Japan; Taiwan (Province of China); Bolivia (Plurinational State of); New Zealand; Senegal; Italy; Antarctica; Ethiopia; Macedonia (the former Yugoslav Republic of); Afghanistan; Russian Federation; Czechia; United States of America; Egypt; Saudi Arabia; Pakistan; China; Ireland; Slovakia; France; Lithuania; Serbia; Kyrgyzstan; Romania; Philippines; Rwanda; Uzbekistan; Bangladesh; Nicaragua; Norway; Dominican Republic; Mexico; Uganda; Zimbabwe; Greenland; Indonesia

Care

Exercise care when cleaning your actinolite. A soft cloth should keep it looking its best.

More About Actinolite

Although actinolite is prevalent worldwide, there isn't much folklore that surrounds it. Those who believe in the metaphysical believe that actinolite balances body, mind, and spirit.

Species/Variety

Smaragdite

Smaragdite is the emerald green variety of actinolite. The name comes from the Latin word "Smaragdos" that means green. It gets its green color from trace amounts of chromium.

  • Classification
  • Characteristic Physical properties
Common Name
Smaragdite
Specific Gravity
3.24

Optical Phenomena

Cat's Eye

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case actinolite. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light throughout the crystal, scattering and reflecting light back to the viewer as a thin line.

Cat's Eye Actinolite
Cat's Eye Actinolite
  • Classification
Common Name
Cat's Eye
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