Actinolite

Actinolite
Actinolite crystal from Portugal
General
CategoryInosilicates
Formula
(repeating unit)
Ca2(Mg4.5-2.5Fe2+0.5-2.5)
Si8O22(OH)2
IMA symbolAct[1]
Strunz classification9.DE.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Identification
Colorpale to dark green, yellowish green, blue and black. White or grey when in asbestos
Crystal habitbladed, fibrous, radial
Twinningsimple or lamellar
Cleavageperfect along {110}.
Fractureuneven
Mohs scale hardness5–6
Lustervitreous to dull
Streakwhite
Diaphaneitytranslucent to transparent
Specific gravity3.00 (+0.10, -0.05)
Polish lustervitreous
Optical propertiesBiaxial (−)
Refractive indexnα = 1.613–1.628
nβ = 1.627–1.644
nγ = 1.638–1.655
Birefringence0.0250–0.0270
Pleochroismmoderate, yellow to dark green (in stones that are transparent)
2V angle78–82° (calc), 84–73° (meas)
Dispersionr < v
Ultraviolet fluorescenceinert
Absorption spectrafaint line at 503 nm
References[2][3][4][5][6]

Actinolite is an amphibole silicate mineral with the chemical formula Ca2(Mg4.5–2.5Fe2+0.5–2.5)Si8O22(OH)2.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Actinolite. Mindat.org
  3. ^ Actinolite. Webmineral.org
  4. ^ Actinolite. Handbook of mineralogy
  5. ^ Gem Reference Guide. City: Gemological Institute of America (GIA), 1988. ISBN 0-87311-019-6
  6. ^ IMA Master List