actinolite

{{Infobox mineral |boxbgcolor=#987630| name = Actinolite | boxtextcolor = #fff | category = Inosilicates | image = Actinolite Portugal.jpg | imagesize = 260px | alt = | caption = Actinolite crystal from Portugal | formula = Ca2(Mg4.5-2.5Fe2+0.5-2.5) Si8O22(OH)2 |IMAsymbol=Act | molweight = | strunz = 9.DE.10 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m | color = pale to dark green, yellowish green, blue and black. White or grey when in asbestos | habit = bladed, fibrous, radial | twinning = simple or lamellar | cleavage = perfect along {110}. | fracture = uneven | mohs = 5–6 | luster = vitreous to dull | polish = vitreous | refractive = nα = 1.613–1.628 nβ = 1.627–1.644 nγ = 1.638–1.655 | opticalprop = Biaxial (−) | 2V = 78–82° (calc), 84–73° (meas) | dispersion = r < v | birefringence = 0.0250–0.0270 | pleochroism = moderate, yellow to dark green (in stones that are transparent) | fluorescence= inert | absorption = faint line at 503 nm | streak = white | gravity = 3.00 (+0.10, -0.05) | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = translucent to transparent | other = |references = }}

thumb|upright=0.3|Gem-quality actinolite blade, from Mogok, Burma