Actinolite is a unique mineral, with an attractive deep-green color. This green color is the result of iron in its chemical lattice. The amount of iron varies among specimens, creating a varying contrast of green; more iron will give a specimen a darker color, even black. This deep-green mineral is associated with numerous other minerals, including Quartz, Talc, Calcite, Albite, Epidote, and Magnetite, to name a few.

The crystal system for Actinolite is monoclinic, though it rarely forms distinct stand-alone crystals. In most occurrences it is found as elongated prismatic crystals, often in bladed groups. These bladed crystal clusters are often embedded/included in Quartz or Talc. Other crystal forms include fibrous, acicular, radiating, in hairlike masses, and in tight interlocking fibers which can appear massive. These crystals are rarely transparent, but more often translucent, with a silky to vitreous luster.

Actinolite can be found in numerous locations, with noteworthy locatlities including Canada, Italy, Norway, Pakistan, Poland and the USA (Colorado, Pennsylvania, Vermont and Washington).