The name actinolite is derived from the Greek word aktis (ἀκτίς), meaning "beam" or "ray", because of the mineral's fibrous nature.

[3] Actinolite is an intermediate member in a solid-solution series between magnesium-rich tremolite, Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2, and iron-rich ferro-actinolite, ☐Ca2(Mg2.5-0.0Fe2+2.5-5.0)Si8O22(OH)2.

The old mineral name uralite is at times applied to an alteration product of primary pyroxene by a mixture composed largely of actinolite.

The metamorphosed gabbro or diabase rock bodies, referred to as epidiorite, contain a considerable amount of this uralitic alteration.

Fibrous actinolite is one of the six recognised types of asbestos, the fibres being so small that they can enter the lungs and damage the alveoli.