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Actinolite

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Formula:
☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
System:
Monoclinic
Colour:
Green, green-black, ...
Lustre:
Vitreous, Silky
Hardness:
5 - 6
Name:
Named in 1794 by Richard Kirwan from the Greek ακτίνα ("aktina") for "ray" and λίθος ("lithos") for "stone" in allusion to the fibrous nature of the original specimens.


Note: Tremolite is defined as having an Mg/(Mg+Fe2+) ratio ≥ 0.9; actinolite has a ratio of 0.5–0.9 and ferro-actinolite has a ratio of less than 0.5. The name actinolite was retained in the nomenclature, since it is entrenched in the literature.

As bladed crystals, to 15 cm; columnar, may be kinked or bent; radiating fibrous to asbestiform; granular to massive.

Visit gemdat.org for gemological information about Actinolite.

Classification of Actinolite

Approved, 'Grandfathered' (first described prior to 1959)
9.DE.10

9 : SILICATES (Germanates)
D : Inosilicates
E : Inosilicates with 2-periodic double chains, Si4O11; Clinoamphiboles
14.23.2

14 : Silicates not Containing Aluminum
23 : Silicates of Fe, Mg, Ca
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http://www.mindat.org/min-18.html
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Occurrences of Actinolite

Geological Setting:
Produced by low-grade regional or contact metamorphism of magnesium carbonate, mafic, or ultramafic rocks; Also in glaucophane-bearing blueschists.

Occurs in many localities. In Austria, on Mt. Greiner, Zillertal, and at Untersulzbachtal. From Zermatt, Valais, Switzerland. At Snarum and Arendal, Norway. From the Ural Mountains, Russia. In the USA, from Gouverneur, St. Lawrence Co., New York; Franklin and Newton, Sussex Co., New Jersey; Chester, Windsor Co., Vermont; in the Fairfax quarry, Centreville, Fairfax Co., Virginia; Crestmore, Riverside Co., California; at Salida, Cha®ee Co., Colorado. Nephrite jade occurs, in the USA, south and east of Lander, Fremont Co., Wyoming; north from Cape San Martin, Monterey Co., California; and around Jade Mountain, near the Kobuk River, Alaska. Along the Fraser River, British Columbia, Canada. Around Mt. Cook, South Island, New Zealand. Fine material from the Kunlun Mountains, Sinkiang Uighur Autonomous Region, China.

Physical Properties of Actinolite

Vitreous, Silky
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Green, green-black, grey-green, or black
Comment:
Colourless, pale green to deep green in thin section.
Streak:
White
Hardness (Mohs):
5 - 6
Hardness Data:
Measured
Tenacity:
Brittle
Cleavage:
Distinct/Good
on {110}
Parting:
on {100}
Fracture:
Splintery
Density:
3.03 - 3.24 g/cm3 (Measured)    3.07 g/cm3 (Calculated)

Crystallography of Actinolite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Space Group Setting:
C2/m
Cell Parameters:
a = 9.891Å, b = 18.2Å, c = 5.31Å
β = 104.64°
Ratio:
a:b:c = 0.543 : 1 : 0.292
Unit Cell Volume:
V 924.85 ų (Calculated from Unit Cell)
Z:
2
Twinning:
simple or lamellar, common parallel {100}; lamellar, less common parallel {001}
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
8.47 (70)
5.305 (10)
4.91 (70)
3.401 (80)
3.143 (70)
2.719 (100)
2.543 (100)
Comments:
ICDD 25-0157

Optical Data of Actinolite

Type:
Biaxial (-)
RI values:
nα = 1.613 - 1.646 nβ = 1.624 - 1.656 nγ = 1.636 - 1.666
2V:
Measured: 79° to 86°, Calculated: 78° to 82°
Max Birefringence:
δ = 0.023
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r < v
Pleochroism:
Weak
Comments:
X= pale yellow, yellowish green
Y= pale yellow-gree, green
Z= pale green, deep greenish blue

Chemical Properties of Actinolite

Formula:
☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Idealised Formula:
☐{Ca2}{(Mg,Fe2+)5}(Si8O22)(OH)2
All elements listed in formula:
Common Impurities:
Mn,Al,Na,K,Ti

Relationship of Actinolite to other Species

Series:
Forms a series with Tremolite (see here)
Forms a series with Ferro-actinolite (see here)
Other Members of Group:
Ferro-actinolite☐{Ca2}{Fe52+}(Si8O22)(OH)2
Ferro-fluoro-actinolite☐{Ca2}{Fe5}(Si8O22)F2
Fluoro-tremolite☐{Ca2}{Mg5}(Si8O22)F2
Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2
9.DE.05Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
9.DE.05Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
9.DE.05Clino-holmquistite Root Name☐{Li2}{Z32+Z23+}(Si8O22)(OH,F,Cl)2
9.DE.05Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
9.DE.05Manganocummingtonite☐{Mn22+}{Mg5}(Si8O22)(OH)2
9.DE.05Manganogrunerite☐{Mn22+}{Fe52+}(Si8O22)(OH)2
9.DE.05Permanganogrunerite☐{Mn22+}{Mn52+}(Si8O22)(OH)2
9.DE.05Ferro-fluoro-pedrizite{Na}{Li2}{Fe2Al2Li}(Al2Si6O22)F2
9.DE.05Ferri-fluoro-leakeite{Na}{Na2}{Mg2Fe23+Li}(Si8O22)F2
9.DE.10Ferri-tschermakite☐{Ca2}{Mg3Fe23+}(Al2Si6O22)(OH)2
9.DE.10Ferro-actinolite☐{Ca2}{Fe52+}(Si8O22)(OH)2
9.DE.10Ferro-hornblende☐{Ca2}{Fe42+Al}(AlSi7O22)(OH)2
9.DE.10Ferro-tschermakite☐{Ca2}{Fe32+Al2}(Al2Si6O22)(OH)2
9.DE.10Joesmithite{Pb}{Ca2}{Mg3Fe23+}(Be2Si6O22)(OH)2
9.DE.10Magnesio-hornblende☐{Ca2}{Mg4Al}(AlSi7O22)(OH)2
9.DE.10Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2
9.DE.10Tschermakite☐(Ca2)(Mg3Al2)(Al2Si6O22)(OH)2
9.DE.10CannilloiteCa(Ca2)(Mg4Al)(Al3Si5O22)(OH)2
9.DE.10Fluoro-cannilloite{Ca}{Ca2}{Mg4Al}(Al3Si5O22)(F,OH)2
9.DE.10Parvo-manganotremolite☐{CaMn2+}{Mg5}(Si8O22)(OH)2
9.DE.10Fluoro-tremolite☐{Ca2}{Mg5}(Si8O22)F2
9.DE.10Potassic-fluoro-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)F2
9.DE.15Edenite{Na}{Ca2}{Mg5}(AlSi7O22)(OH)2
9.DE.15Ferro-edenite{Na}{Ca2}{Fe52+}(AlSi7O22)(OH)2
9.DE.15Ferro-kaersutite{Na}{Ca2}{Fe32+AlTi}(Al2Si6O22)O2
9.DE.15Ferro-pargasite{Na}{Ca2}{Fe42+Al}(Al2Si6O22)(OH)2
9.DE.15Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
9.DE.15Kaersutite{Na}{Ca2}{Mg3AlTi}(Al2Si6O22)O2
9.DE.15Magnesio-hastingsite{Na}{Ca2}{Mg4Fe3+}(Al2Si6O22)(OH)2
9.DE.15Pargasite{Na}{Ca2}{Mg4Al}(Al2Si6O22)(OH)2
9.DE.15Sadanagaite{Na}{Ca2}{Mg3Al2}(Si5Al3O22)(OH)2
9.DE.15Fluoro-edenite{Na}{Ca2}{Mg5}(AlSi7O22)(F,OH)2
9.DE.15Potassic-ferro-ferri-sadanagaite{K}{Ca2}{Fe32+Fe23+}(Al3Si5O22)(OH)2
9.DE.15Potassic-sadanagaite{K}{Ca2}{Mg3Al2}(Al3Si5O22)(OH)2
9.DE.15Potassic-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)(OH)2
9.DE.15Potassic-ferro-sadanagaite{K}{Ca2}{Fe32+Al2}(Al3Si5O22)(OH)2
9.DE.15Magnesio-fluoro-hastingsite{Na}{Ca2}{Mg4Fe3+}(Al2Si6O22)F2
9.DE.15Potassic-fluoro-hastingsite{K}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(F,OH)2
9.DE.15Potassic-chloro-hastingsite{K}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(Cl,OH)2
9.DE.15Fluoro-pargasite{Na}{Ca2}{Mg4Al}(Al2Si6O22)(F,OH)2
9.DE.15Parvo-mangano-edenite{Na}{CaMn2+}{Mg5}(AlSi7O22)(OH)2
9.DE.15Potassic-chloro-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)(Cl,OH)2
9.DE.15Potassic-ferro-chloro-edenite{K}{Ca2}{Fe52+}(AlSi7O22)(Cl,OH)2
9.DE.15Potassic-magnesio-hastingsite{K}{Ca2}{Mg4Fe3+}(Al2Si6O22)(OH)2
9.DE.15Potassic-ferro-pargasite{K}{Ca2}{Fe42+Al}(Al2Si6O22)(OH)2
9.DE.15Chromio-pargasite{Na}{Ca2}{Mg4Cr3+}(Al2Si6O22)(OH)2
9.DE.20Ferro-taramiteNa(CaNa)(Fe32+Al2)(Al2Si6O22)(OH)2
9.DE.20Barroisite☐{CaNa}{Mg3Al2}(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-barroisite☐(CaNa)(Fe32+Fe23+)(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-winchite☐[CaNa][Fe42+(Fe3+,Al)]Si8O22(OH)2
9.DE.20Ferri-barroisite☐(CaNa)(Mg3Fe23+)(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-taramiteNa(CaNa)(Fe32+Fe23+)(Al2Si6O22)(OH)2
9.DE.20Ferro-ferri-katophoriteNa(NaCa)(Fe42+Fe3+)(Si7Al)O22(OH)2
9.DE.20Ferro-barroisite☐{CaNa}{Fe32+Al2}(AlSi7O22)(OH)2
9.DE.20Ferro-richterite{Na}{CaNa}{Fe52+}(Si8O22)(OH)2
9.DE.20Ferro-winchite ☐{CaNa}{Fe42+Al}(Si8O22)(OH)2
9.DE.20Ferro-katophorite{Na}{CaNa}{Fe42+Al}[(AlSi7)O22](OH)2
9.DE.20Ferri-taramiteNa(CaNa)(Mg3Fe23+)(Al2Si6O22)(OH)2
9.DE.20Magnesiotaramite{Na}{CaNa}{Mg3AlFe3+}(Al2Si6O22)(OH)2
9.DE.20Richterite{Na}{NaCa}{Mg5}(Si8O22)(OH)2
9.DE.20Winchite☐{CaNa}{Mg4Al}(Si8O22)(OH)2
9.DE.20Taramite{Na}{CaNa}{Mg3Al2}(Al2Si6O22)(OH)2
9.DE.20Fluoro-richterite{Na}{CaNa}{Mg5}(Si8O22)(F,OH)2
9.DE.20Katophorite{Na}{CaNa}{Mg4Al}[(AlSi7)O22](OH)2
9.DE.20Potassic-fluoro-richterite{K}{CaNa}{Mg5}(Si8O22)(F,OH)2
9.DE.20Potassic-richteriteK[CaNa][Mg5]Si8O22(OH)2
9.DE.20Ferri-ghoseite☐[Mn2+Na][Mg4Fe3+]Si8O22(OH)2
9.DE.20Ferri-winchite☐[CaNa][Mg4(Fe3+,Al)]Si8O22(OH)2
9.DE.20Fluoro-taramite{Na}{CaNa}{Mg3Al2}(Al2Si6O22)F2
9.DE.25Arfvedsonite[Na][Na2][Fe42+Fe3+]Si8O22(OH)2
9.DE.25EckermanniteNaNa2(Mg4Al}Si8O22(OH)2
9.DE.25Ferro-eckermanniteNaNa2(Fe42+Al)Si8O22(OH)2
9.DE.25Ferro-glaucophane◻[Na2][Fe32+Al2]Si8O22(OH)2
9.DE.25Glaucophane◻[Na2][Mg3Al2]Si8O22(OH)2
9.DE.25Potassic-mangani-leakeite[(Na,K)][Na2][Mg2Mn23+Li]Si8O22(OH)2
9.DE.25Mangano-ferri-eckermannite[Na][Na2][Mn42+(Fe3+)]Si8O22(OH)2
9.DE.25Ferri-leakeite[Na][Na2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Magnesio-riebeckite◻{Na2}{Mg3Fe23+}(Si8O22)(OH)2
9.DE.25Magnesio-arfvedsonite{Na}{Na2}{Mg4Fe3+}(Si8O22)(OH)2
9.DE.25NybøiteNaNa2(Mg3Al2)(AlSi7O22)(OH)2
9.DE.25Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
9.DE.25Mangano-mangani-ungarettiiteNaNa2(Mn22+Mn33+)(Si8O22)O2
9.DE.25Ferro-ferri-nybøiteNaNa2[(Fe32+,Mg)Fe23+](AlSi7O22)(OH)2
9.DE.25Clino-ferro-ferri-holmquistite◻{Li2}{Fe32+Fe23+}(Si8O22)(OH)2
9.DE.25Ferri-nybøiteNaNa2(Mg3Fe23+](AlSi7O22)(OH)2
9.DE.25Ferro-ferri-leakeite[Na][Na2][Fe22+Fe23+Li]Si8O22(OH)2
9.DE.25Ferro-ferri-fluoro-leakeiteNa(Na2)(Fe22+Fe23+Li)(Si8O22)(F)2
9.DE.25Sodic-ferri-clinoferroholmquistiteNa0.5{Li2}{Fe32+Fe23+}(Si8O22)(OH)2
9.DE.25Magnesio-fluoro-arfvedsonite[Na][Na2][Mg4Fe3+][Si8O22](F,OH)2
9.DE.25Ferri-pedrizite[Na][Li2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Potassic-ferri-leakeite[K][Na2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Fluoro-nybøiteNaNa2(Mg3Al2)(AlSi7O22)(F,OH)2
9.DE.25Mangani-dellaventuraite{Na}{Na2}{MgMn23+LiTi4+}Si8O22O2
9.DE.25Fluoro-pedriziteNaLi2(Mg2Al2Li)(Si8O22)F2
9.DE.25Potassic-arfvedsonite[(K,Na)][Na2][Fe42+Fe3+]Si8O22(OH)2
9.DE.25Mangani-obertiiteNa(Na2)(Mg3Mn3+Ti)(Si8O22)O2
9.DE.25Potassic-magnesio-fluoro-arfvedsonite[(K,Na)][Na2][Mg4Fe3+][Si8O22][(F,OH)2]
9.DE.25Ferro-ferri-pedrizite[Na][Li2][Fe22+Fe23+Li]Si8O22(OH)2
9.DE.25Potassic-magnesio-arfvedsonite[K][Na2][Mg4Fe3+]Si8O22(OH)2
9.DE.25PedriziteNaLi2(LiMg2Al2)(Si8O22)(OH)2
9.DE.25Ferro-pedriziteNaLi2(Fe22+Al2Li)Si8O22(OH)2
9.DE.25Fluoro-leakeiteNaNa2(Mg2Al2Li)(Si8O22)F2
9.DE.25Ferro-ferri-obertiiteNaNa2(Fe32+Fe3+Ti)Si8O22O2
14.23.1Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6

Other Names for Actinolite

Other Information

Health Risks:
Dust from asbestiform varieties of actinolite can cause serious and irreversible lung disease when inhaled. Avoid creating or inhaling dust.

References for Actinolite

Reference List:
Kirwan, R. (1794) 16th species: actynolite. in Elements of Mineralogy, 2nd Edition, Volume 1, Elmsly (London) 167-170.

Hawthorne, F.C. (1983) The crystal chemistry of the amphiboles; Introduction. The Canadian Mineralogist: 21: 174.

Hawthorne, F.C. (1983) The crystal chemistry of the amphiboles; Classification and nomenclature. The Canadian Mineralogist: 21: 175-176.

Mandarino, J.A. (1998) The Second List of Additions and Corrections to the Glossary of Mineral Species (1995). The Amphibole Group. Mineralogical Record: 29: 169-174.

Hawthorne, F.C., Oberti, R. (2006) On the classification of amphiboles. The Canadian Mineralogist: 44: 1-21.


Internet Links for Actinolite

Specimens:
The following Actinolite specimens are currently listed for sale on minfind.com.

Localities for Actinolite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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