Actinolite is an amphibole silicate mineral with the chemical formula .

Etymology

The name ''actinolite'' is derived from the Greek word ''aktis'' (), meaning "beam" or "ray", because of the mineral's fibrous nature.

Mineralogy

Actinolite is an intermediate member in a solid-solution series between magnesium-rich tremolite, , and iron-rich ferro-actinolite, . Mg and Fe ions can be freely exchanged in the

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

structure. Like tremolite, asbestiform actinolite is regulated as asbestos.

Occurrence

Actinolite is commonly found in metamorphic rocks, such as contact aureoles surrounding cooled intrusive igneous rocks. It also occurs as a product of

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

of magnesium-rich

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

s. The old mineral name ''uralite'' is at times applied to an alteration product of primary pyroxene by a mixture composed largely of actinolite. The metamorphosed gabbro or diabase rock bodies, referred to as epidiorite, contain a considerable amount of this ''uralitic'' alteration. Fibrous actinolite is one of the six recognised types of asbestos, the fibres being so small that they can enter the

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

s and damage the alveoli. Actinolite asbestos was once mined along Jones Creek at Gundagai, Australia.

Gemology

Some forms of actinolite are used as

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

s. One is nephrite, one of the two types of jade (the other being jadeite, a variety of pyroxene). Another gem variety is the chatoyant form known as ''cat's-eye actinolite''. This stone is translucent to opaque, and green to yellowish green color. This variety has had the misnomer ''jade cat's-eye''. Transparent actinolite is rare and is faceted for gem collectors. Major sources for these forms of actinolite are

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

and

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. Other sources are

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

, and the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

References

* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York {{Commons category Inosilicates Calcium minerals Magnesium minerals Iron(II) minerals Asbestos Amphibole group Monoclinic minerals Minerals in space group 12 Gemstones

Etymology

Mineralogy

Occurrence

Gemology

See also

References