Actinolite crystals with talc. Actinolite (long filaments) is an amphibole silicate mineral (monoclinic). It is typically pale to dark green and occurs as long fibrous, often radial crystals in low to medium grade metamorphic rocks. It is often associated with other fibrous minerals, like the talc (talcum, hydrous magnesium silicate) with which it is intermixed in this sample. Specimen found in the Tirol, Austria.