Mineral
Ferroactinolita
Ca₂Fe²⁺₅Si₈O₂₂(OH)₂ · Silicatos (Inosilicatos)
Ferro-actinolite, Ca₂Fe²⁺₅Si₈O₂₂(OH)₂, represents the iron-rich end member of the tremolite–actinolite series. It is the ferriferous counterpart of actinolite: the dominance of iron accounts for its higher density and its very dark green, greenish-brown or black tones. It usually occurs as prismatic or acicular crystals, or as fibrous aggregates, with a heavier and darker appearance than common actinolite.
Etymology
From the latin ferrum and actinolite; iron rich on the series