Original description: ‘Actynolite’ Kirwan, R., 1794. 16th Species: Lamellar Actynolite — Elements of Mineralogy, Elmsly, London: 167 [
view in ‘Library’].
Type locality: unknown.
Type material: unknown.
Etymology: from the Greek words
ακτίνα (aktina) for ‘ray’ and
λίθος (lithos) for ‘stone’, in allusion to the fibrous nature of the original specimens.
Distribution: Austria: Zillertal; China: Kunlun Mountains; Russia: Urals; Switzerland: from Zermatt, Valais (
Anthony et al., 2001—2005).
Chemistry
Ca2(Mg,Fe)5Si8O22(OH)2
Essential elements: hydrogen (H), oxygen (O), magnesium (Mg), silicon (Si), calcium (Ca), iron (Fe).
Crystal data
Crystallography: monoclinic — prismatic.
Crystal habit: as bladed crystals, to 15 cm; columnar, may be kinked; granular to massive.
Twinning: simple or lamellar (
Anthony et al., 2001—2005).
Optical properties
Colour: bright green to greyish green; in thin section, colourless, pale green to deep green (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent (
Anthony et al., 2001—2005).
Lustre: vitreous (
Anthony et al., 2001—2005).
Refractive index: 1.6—1.63 — anisotropic [biaxial (-)] (
Lazzarelli, 2012).
Birefringence: 0.03.
Dispersion: none.
Pleochroism: weak; X = pale yellow, yellowish green; Y = pale yellow-green, green; Z = pale green, deep greenish blue (
Anthony et al., 2001—2005).
Material from ‘Repository’
