Editing Amphibole (section)

===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>