Actinolite

Massive, dark green, coarse-grained actinolite with pink rhodonite and white calcite from the “genthelvite pit” adjacent to the footwall of the east limb of ore at Sterling Hill. At least four chemical analyses have been made of actinolite specimens from this pit, all of which support the identity of the dark green amphibole as zincian, manganoan actinolite. The most rigorous analysis, that of Craig and Moritz (2024), shows a content of 7.74 wt.% ZnO and 4.39 wt.% MnO. As discussed in Leavens et al. (2009), the actinolite and rhodonite in this area are retrograde metamorphic products formed by recrystallization of an original high-temperature assemblage with augite, calcite, bustamite, and garnet as the major phases originally present.

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