Image: Andrew Silver (Public domain)
monocliniccommonSilicates (Amphibole Group)
Actinolite
Ca2(Mg,Fe)5Si8O22(OH)2
The image displays a dark green, bladed to prismatic aggregate of actinolite crystals, showing a somewhat fibrous texture typical of its amphibole structure.
Actinolite Physical Properties
Mohs Hardness
5.5Crystal System
monoclinicLuster
vitreousStreak Color
whiteCleavage
perfect on {110} at 56° and 124°Fracture
unevenSpecific Gravity
3.2Colors
green, dark green, blackish green, white, grayTransparency
translucentType Locality
Widespread in metamorphic terrains globally, e.g., Switzerland, Austria, USA (California, Vermont)Mineral Group
Silicates (Amphibole Group)Uses
gemstone (as nephrite jade), collector's specimens, historically as asbestos (fibrous varieties)Associated Minerals
chlorite, epidote, garnet, talc, quartz, albiteRarity
commonGeological Context
Actinolite forms primarily in metamorphic rocks, especially in greenschist facies, often resulting from the alteration of mafic igneous rocks or magnesium-rich sedimentary rocks.
