Actinolite

Actinolite is an inosilicate[?] mineral with the chemical formula Ca₂(Mg, Fe)₅Si₈O₂₂(OH)₂

Table of contents showTocToggle("show","hide") 1 Mineralogy 2 Occurrence 3 Details 4 Related minerals

Mineralogy

Actinolite is an intermediate member in a series between tremolite[?] (Mg-rich) and ferro-actinolite[?] (Fe-rich). As seen from the chemical formula above, Mg and Fe ions can be freely exchanged in the crystal structure.

Occurrence

Actinolite is commonly found in metamorphic rocks, such as contact aureoles[?] surrounding cooled intrusive igneous rocks. It is also found in magnesium-rich limestones.

Some forms of asbestos are formed from fibrous actinolite, the fibres being so small that they can enter the lungs and damage the alveoli. Another form of actinolite, known as nephrite, is one of the two common constituents of jade (the other being jadeite[?]).

Details

Crystallographic system	Monoclinic
Colours	Pale to dark green. White or grey when in asbestos form
Lustre	Vitreous to dull glassy
Hardness	5.5-6
Refractive index	1.61
Cleavage	2
Pleochroism	Yellow to dark green to transparent to opaque

Related minerals

1. Tremolite[?]
2. Nephrite[?]