Actinolite (Var. Byssolite)
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 3.0)
Mineral NameActinolite (Var. Byssolite)
Chemical FormulaCa2(Mg,Fe2+)5Si8O22(OH)2
Mohs Hardness5.5
Crystal Systemmonoclinic
Lustersilky
Streak Colorwhite
Cleavageperfect on {110}
Fractureuneven
Specific Gravity3
Colorsgrayish-green, yellowish-green
Transparencytranslucent
Type LocalityAure Valley, Hautes-Pyrénées, Midi-Pyrénées, France
Mineral Groupsilicates
Usescollector
Associated Mineralsquartz
Rarityuncommon
Description
This specimen displays delicate, hair-like to fibrous aggregates of byssolite, ranging from pale grayish-green to yellowish-green, growing on a matrix of small, clear to milky quartz crystals.
Geological Context
Actinolite typically forms in metamorphic rocks, such as schists and contact metamorphic zones, often from the alteration of mafic igneous rocks or magnesium-rich limestones. Byssolite is a fibrous variety found in veins or cavities.
