Actinolite thin section
From Greek for ray, in allusion to its frequent occurrence in bundles of radiating needles.
Formula: ▯Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2
System: Monoclinic
Color: Green, green-black, grey-green, or black
Lustre: Vitreous, Silky
Hardness:...