Editing Actinolite

{{Short description|Mineral}}
{{about|the mineral|the community in Canada|Actinolite, Ontario}}
{{redirect|Uralite|the rail stop|Uralite Halt railway station}}
{{Infobox mineral
|boxbgcolor=#987630| name        = Actinolite
| boxtextcolor = #fff
| category    = [[Inosilicates]]
| image       = Actinolite Portugal.jpg
| imagesize   = 260px
| alt         = 
| caption     = Actinolite crystal from [[Portugal]]
| formula     = Ca<sub>2</sub>(Mg<sub>4.5-2.5</sub>Fe<sup>2+</sup><sub>0.5-2.5</sub>) <br/>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>
|IMAsymbol=Act<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| molweight   = 
| strunz      = 9.DE.10
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''C2/m''
| color       = pale to dark green, yellowish green, blue and black. White or grey when in asbestos 
| habit       = bladed, fibrous, radial
| twinning    = simple or lamellar
| cleavage    = perfect along {110}. 
| fracture    = uneven
| mohs        = 5–6
| luster      = vitreous to dull
| polish      = vitreous 
| refractive  = n<sub>α</sub> = 1.613–1.628<br/> n<sub>β</sub> = 1.627–1.644<br/> n<sub>γ</sub> = 1.638–1.655
| opticalprop = Biaxial (−) 
| 2V = 78–82° (calc), 84–73° (meas)
| dispersion = r < v
| birefringence = 0.0250–0.0270
| pleochroism = moderate, yellow to dark green (in stones that are transparent)
| fluorescence= inert
| absorption  = faint line at 503 nm
| streak      = white
| gravity     = 3.00 (+0.10, -0.05)
| density     = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| diaphaneity = translucent to transparent
| other       = 
|references = <ref>[http://www.mindat.org/min-18.html Actinolite]. Mindat.org</ref><ref name=wembmin>[http://www.webmineral.com/data/Actinolite.shtml Actinolite]. Webmineral.org</ref><ref>[http://rruff.geo.arizona.edu/doclib/hom/actinolite.pdf Actinolite]. Handbook of mineralogy</ref><ref name="GRG">Gem Reference Guide. City: [[Gemological Institute of America]] (GIA), 1988. {{ISBN|0-87311-019-6}}</ref><ref>[http://pubsites.uws.edu.au/ima-cnmnc/ IMA Master List]</ref>
}}

'''Actinolite''' is an [[amphibole]] [[silicate minerals|silicate mineral]] with the chemical formula {{nowrap|Ca<sub>2</sub>(Mg<sub>4.5–2.5</sub>Fe<sup>2+</sup><sub>0.5–2.5</sub>)Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>}}.

==Etymology==
The name ''actinolite'' is derived from the [[Greek language|Greek]] word ''aktis'' ({{lang|grc|ἀκτίς}}), meaning "beam" or "ray", because of the mineral's fibrous nature.<ref name=wembmin/>

==Mineralogy==
Actinolite is an intermediate member in a [[Solid solution|solid-solution]] series between magnesium-rich [[tremolite]], {{nowrap|Ca<sub>2</sub>(Mg<sub>5.0-4.5</sub>Fe<sup>2+</sup><sub>0.0-0.5</sub>)Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>}}, and iron-rich [[ferro-actinolite]], {{nowrap|☐Ca<sub>2</sub>(Mg<sub>2.5-0.0</sub>Fe<sup>2+</sup><sub>2.5-5.0</sub>)Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>}}. Mg and Fe [[ion]]s can be freely exchanged in the [[crystal]] structure. Like tremolite, [[asbestiform]] actinolite is regulated as [[asbestos]].

==Occurrence==
Actinolite is commonly found in [[metamorphic rock]]s, such as [[Contact metamorphism|contact aureole]]s surrounding cooled [[Intrusive rock|intrusive]] [[igneous rock]]s. It also occurs as a product of [[metamorphism]] of magnesium-rich [[limestone]]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 (geology)|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 [[fibre]]s being so small that they can enter the [[lung]]s and damage the [[Pulmonary alveolus|alveoli]]. Actinolite asbestos was once mined along Jones Creek at [[Gundagai]], Australia.

==Gemology==
Some forms of actinolite are used as [[gemstone]]s. One is [[nephrite]], one of the two types of [[jade]] (the other being [[jadeite]], a variety of pyroxene).<ref name="GRG"/>

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]] and [[Canada]]. Other sources are [[Madagascar]], [[Tanzania]], and the [[United States]].<ref name="GRG"/>

==See also==
{{Portal|Earth sciences}}
* [[Classification of minerals (disambiguation)|Classification of minerals]]
* [[List of minerals]]

==References==
{{Reflist}}
* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York {{ISBN|0-471-80580-7}}
{{Wiktionary}}
{{Commons category}}

[[Category:Inosilicates]]
[[Category:Calcium minerals]]
[[Category:Magnesium minerals]]
[[Category:Iron(II) minerals]]
[[Category:Asbestos]]
[[Category:Amphibole group]]
[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 12]]
[[Category:Gemstones]]