Montijos quarry, Monte Redondo, Leiria, Leiria, Portugal

 {Ca₂}{Mg_4.5-2.5Fe_0.5-2.5}(Si₈O₂₂)(OH)₂ 

Crystal System: monoclinic
Colour: green, green-black, grey-green or black
Lustre: vitreous, silky
Habitus: fibrous
Hardness: 5 - 6
Fracture: splintery
Cleavage: distinct/good on {110}
Density: 3.03 - 3.24  g/cm³
Origin and geological occurrence: it belongs to the amphibole supergroup and forms a series with tremolite and ferro-actinolite. The Mg end-member (Mg > 4.5 apfu) is called tremolite. Actinolite is produced by low-grade regional or contact metamorphism of magnesium carbonate, mafic or ultramafic rocks; also in glaucophane-bearing blueschists.

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Samples:

	9D.10  Actinolite  Greenish acicular crystals, forming radial aggregates.  #inosilicates
	9D.11 Actinolite Green tabular crystals in schist.  #inosilicates
	9D.13 Actinolite Actinolite-tremolite, whitish fibrous crystals. #inosilicates