Actinolite is an amphibole mineral. Tremolite and Actinolite are identical minerals; their chemical formulae are alike, with a combination of iron and magnesium. They combine together and form a series of magnesium iron silicate minerals. The iron content in the Actinolite mineral is more than that of magnesium whereas in Tremolite, the magnesium is more than iron. It is the iron in the chemical formulae that gives the green color to the Actinolite. The iron content differs with specimens, leading to different shades of green. The darker color of the specimen is in accord of the higher content of iron.

In Quartz crystals, we at times observe inclusions of thin splinters. Parallel and closely packed inclusions leads to the formation of "Chatoyancy"(optical reflectance displayed by some gemstones belonging to the quartz category).

Chemical Formula

Ca₂ (Mg_{4. 5-2.5}Fe²⁺_0.5-2.5) Si₈O₂₂ (OH) ₂.

Derivation Of Name

Its name derives from the Greek word "aktis", expressed as "aktic", which means ray or "bean", on account of the fibrous nature of the mineral. The word "aktic" originates from the name given to this chemical element.

Occurrence

Actinolite is generally seen in metamorphic rocks, like the igneous rocks that are surrounded with cool intrusions. Another way of occurrence is when limestone rich in magnesium metamorphoses. Of the 6 varieties of asbestos, Actinolite is one among them. The asbestos content is very minute and can get into the lungs and harm the alveoli. It was in Australia at Gundagai that Actinolite was at a time mined in Jones Creek.

Gemology

Certain gemstones are made from Actinolite of different forms. Nephrite is one among them which belongs to one among the two varieties of jade (and the other is jadeite, a type of Pyroxene). The other variety of gems are of the Chatoyant form, called cat's-eye Actinolite. This particular stone varies from green to yellow in color and opaque to translucent.

Source

Transparent Actinolite is rare and is faceted for gem collectors. Major sources for these forms of Actinolite are Taiwan and Canada. Other sources are Madagascar, Tanzania, and the United States.

Mineralogy

Actinolite is obtained in the series of a solid-solution in the transitional stage from tremolite rich in magnesium to ferro-actinolite, rich in iron,

Color Green, gray-green, green-black or black

Density 3.07 g/cm³