Main Page | See live article | Alphabetical index Actinolite is an inosilicate mineral with the chemical formula Ca2(Mg, Fe)5Si8O22(OH)2 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 Tremolite Nephrite This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.