Editing Amphibole (section)

==Mineral species==
The more common amphiboles are classified as shown in the following table:{{sfn|Nesse|2000|p=278}}
{| class="wikitable" style="text-align: left;"
! colspan=8 | Amphibole classification (After Nesse 2000{{sfn|Nesse|2000|p=278}})
|-
! Group
! W
! {{chem2|X2}}
! {{chem2|Y5}}
! {{chem2|Z8O22(OH)2}}
! Mineral
! Symmetry
! Comment
|-
|rowspan=3| Iron-magnesium 
| 
| {{chem2|(Mg,Fe)2}}
| {{chem2|(Mg,Fe)5}}
| {{chem2|Si8O22(OH)2}}
| [[Anthophyllite]] 
|rowspan=2|Orthorhombic
|rowspan=2|Orthoamphibolite
|-
|
| {{chem2|(Mg,Fe)2}}
| {{chem2|(Mg,Fe)3Al2}}
| {{chem2|Al2Si6O22(OH)2}}
| [[Gedrite]]
|-
|
| {{chem2|(Mg,Fe)2}}
| {{chem2|(Mg,Fe)5}}
| {{chem2|Si8O22(OH)2}}
| [[Cummingtonite]]-[[Grunerite]]
| rowspan=8 | Monoclinic
| Low-Ca-clinoamphibolite
|-
| rowspan=3 |Calcic
|
| {{chem2|Ca2}}
| {{chem2|(Mg,Fe)5}}
| {{chem2|Si8O22(OH)2}}
| [[Tremolite]]-[[actinolite]]
| rowspan=3 | Ca-clinoamphibole
|-
| {{chem2|(Na,K)_{0-1}|}}
| {{chem2|Ca2}}
| {{chem2|(Mg,Fe,Fe^{3+},Al)5}}
| {{chem2|(Si,Al)8O22(OH)2}}
| [[Hornblende]]
|-
| {{chem2|Na|}}
| {{chem2|Ca2}}
| {{chem2|(Mg,Fe)4Ti}}
| {{chem2|Si6Al2O22(OH)2}}
| [[Kaersutite]]
|-
| rowspan=2 | Sodic-calcic
| {{chem2|Na|}}
| {{chem2|NaCa}}
| {{chem2|(Mg,Fe)5}}
| {{chem2|Si8O22(OH)2}}
| [[Richterite]]
| rowspan=2 | Na-Ca-clinonamphibole
|-
| {{chem2|Na|}}
| {{chem2|NaCa}}
| {{chem2|(Mg,Fe)4Fe^{3+}|}}
| {{chem2|Si7AlO22(OH)2}}
| [[Katophorite]]
|-
| rowspan=2 |Sodic
|
| {{chem2|Na2|}}
| {{chem2|(Mg,Fe)3(Al,Fe^{3+})2}}
| {{chem2|Si8O22(OH)2}}
| [[Glaucophane]]-[[riebeckite]]
| rowspan=2 | Na-clinoamphibole
|-
| {{chem2|Na|}}
| {{chem2|Na2|}}
| {{chem2|(Mg,Fe)4(Al,Fe^{3+})}}
| {{chem2|Si8O22(OH)2}}
| [[Eckermanite]]-[[arfvedsonite]]
|}

===Other species===
'''Orthorhombic series'''
* [[Holmquistite]], Li<sub>2</sub>Mg<sub>3</sub>Al<sub>2</sub>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>
'''Monoclinic series'''
* [[Pargasite]], NaCa<sub>2</sub>Mg<sub>3</sub>Fe<sup>2+</sup>Si<sub>6</sub>Al<sub>3</sub>O<sub>22</sub>(OH)<sub>2</sub>
* [[Winchite]], (CaNa)Mg<sub>4</sub>(Al,Fe<sup>3+</sup>)Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>
* [[Edenite]], NaCa<sub>2</sub>Mg<sub>5</sub>(Si<sub>7</sub>Al)O<sub>22</sub>(OH)<sub>2</sub>

===Series===
Certain amphibole minerals form solid solution series, at least at elevated temperature. Ferrous iron usually substitutes freely for magnesium in amphiboles to form continuous solid solution series between magnesium-rich and iron-rich endmembers. These include the cummington (magnesium) to grunerite (iron) endmembers, where the dividing line is placed at 30% magnesium.{{sfn|Nesse|2000|pp=277-290}}

In addition, the orthoamphiboles, anthophyllite and gedrite, which differ in their aluminium content, form a continuous solid solution at elevated temperature. As the amphibole cools, the two end members exsolve to form very thin layers (lamellae).{{sfn|Nesse|2000|pp=277-290}}

Hornblende is highly variable in composition, and includes at least five solid solution series: magnesiohornblende-ferrohornblende ({{chem2|Ca2[(Mg,Fe)4Al]Si7AlO22(OH)2}}), tschermakite-ferrotschermakite ({{chem2|Ca2[(Mg,Fe)3Al2]Si6Al2O22(OH)2}}), edenite-ferroedenite ({{chem2|NaCa2(Mg,Fe)5Si7AlO22(OH)2}}), pargasite-ferropargasite ({{chem2|NaCa2[(Mg,Fe)4Al]Si6Al2O22(OH)2}}) and magnesiohastingstite-hastingsite ({{chem2|NaCa2[(Mg,Fe)4Fe^{3+}]Si6Al2O22(OH)2}}). In addition, titanium, manganese, or chromium can substitute for some of the cations and oxygen, fluorine, or chlorine for some of the hydroxide. The different chemical types are almost impossible to distinguish even by optical or X-ray methods, and detailed chemical analysis using an electron microprobe is required.{{sfn|Nesse|2000|p=285}}

Glaucophane to riebeckite form yet another solid solution series, which also extends towards hornblende and arfvedsonite.{{sfn|Nesse|2000|p=287}}

There is ''not'' a continuous series between calcic clinoamphiboles, such as hornblende, and low-calcium amphiboles, such as orthoamphiboles or the cummingtonite-grunerite series. Compositions intermediate in calcium are almost nonexistent in nature.{{sfn|Nesse|2000|p=279}} However, there is a solid solution series between hornblende and tremolite-actinolite at elevated temperature. A [[miscibility gap]] exists at lower temperatures, and, as a result, hornblende often contains exsolution lamellae of grunerite.{{sfn|Klein|Hurlbut|1993|p=496}}

===Descriptions===
On account of the wide variations in chemical composition, the different members vary considerably in properties and general appearance.

[[Anthophyllite]] occurs as brownish, fibrous or lamellar masses with hornblende in [[mica]]-[[schist]] at [[Kongsberg]] in [[Norway]] and some other localities. An aluminous related species is known as [[gedrite]] and a deep green [[Russia]]n variety containing little [[iron]] as [[kupfferite]].<ref name="EB1911"/>

[[Hornblende]] is an important constituent of many igneous rocks. It is also an important constituent of [[amphibolite]]s formed by metamorphism of [[basalt]].{{sfn|Nesse|2000|p=286}}

[[Actinolite]] is an important and common member of the monoclinic series, forming radiating groups of [[Crystal habit|acicular]] crystals of a bright green or greyish-green color. It occurs frequently as a constituent of [[greenschist]]s. The name (from [[Ancient Greek|Greek]] ''ἀκτίς, ἀκτῖνος/aktís, aktînos'', a 'ray' and ''λίθος/líthos'', a 'stone') is a translation of the old [[German language|German]] word ''Strahlstein'' (radiated stone).<ref name="EB1911"/>{{sfn|Klein|Hurlbut|1993|pp=495-496}}

[[Glaucophane]], [[crocidolite]], [[riebeckite]] and [[arfvedsonite]] form a somewhat special group of alkali-amphiboles. The first two are blue fibrous minerals, with glaucophane occurring in [[blueschist]]s and crocidolite (blue asbestos) in ironstone formations, both resulting from dynamo-metamorphic processes. The latter two are dark green minerals, which occur as original constituents of igneous rocks rich in sodium, such as [[nepheline]]-[[syenite]] and [[phonolite]].<ref name="EB1911"/>{{sfn|Nesse|2000|pp=287-289}}

[[Pargasite]] is a rare magnesium-rich variety of hornblende{{sfn|Nesse|2000|p=285}} with essential [[sodium]], usually found in [[ultramafic]] rocks. For instance, it occurs in uncommon [[Mantle (geology)|mantle]] [[xenolith]]s, carried up by [[kimberlite]]. It is hard, dense, black and usually [[Rock microstructure#Crystal shapes|automorphic]], with a red-brown [[pleochroism]] in [[Petrography|petrographic]] [[thin section]].<ref name="Handbook">
 {{cite book |chapter-url=http://www.handbookofmineralogy.org/pdfs/pargasite.pdf
 |url=http://www.handbookofmineralogy.org |title=Handbook of Mineralogy
 |chapter=Pargasite |format=pdf
 |publisher=[[Mineralogical Society of America]] |access-date=2012-12-17
 }}</ref>