Editing Hypersthene

{{Short description|Enstatite var., belonging to the group of orthorhombic pyroxenes}}
{{Infobox mineral
| name        = Hypersthene
| boxbgcolor  =#ab8831 
| boxtextcolor = #fff
| image       = File:Hypersthene - USGS Mineral Specimens 657.jpg
| imagesize   = 300px
| category    = [[Inosilicate]]
| formula     = {{chem2|(Mg,Fe)SiO3}}
| strunz      = 8/F.02-20
| system      = [[Orthorhombic]]
| color       = Gray, brown, or green
| twinning    = On [100]
| cleavage={100} Perfect, {010} Perfect
| fracture=Uneven
| mohs        = 5.5–6
| luster      = Vitreous to pearly
| streak      = Greyish white, greenish 
| gravity     = 3.4–3.9
| opticalprop =Biaxial (−) 
| refractive  =n<sub>α</sub> = 1.669 – 1.755 n<sub>β</sub> = 1.674 – 1.763 n<sub>γ</sub> = 1.680 – 1.773 
| birefringence =δ = 0.011 – 0.018 
| dispersion  = Weak 
}}

'''Hypersthene''' is a common rock-forming [[Silicate minerals|inosilicate]] mineral belonging to the group of [[orthorhombic]] [[pyroxene]]s.<ref name=EB1911>{{EB1911 |wstitle=Hypersthene |volume=14 |page=200 |inline=1 |first=Leonard James |last=Spencer |authorlink=Leonard James Spencer}}</ref> Its chemical formula is {{chem2|(Mg,Fe)SiO3}}. It is found in [[Igneous rock|igneous]] and some [[metamorphic rock]]s as well as in stony and iron [[meteorite]]s. Many references have formally abandoned this term, preferring to categorise this mineral as [[enstatite]] or [[ferrosilite]]. It forms a [[solid solution]] series with the [[mineral]]s enstatite and ferrosilite, being a mid-way member between the two. Pure enstatite contains no iron, while pure ferrosilite contains no magnesium; hypersthene is the name given to the mineral when a significant amount of both elements are present. Enstatite is stable at atmospheric pressure, but ferrosilite is stable only at elevated pressure, decomposing into [[quartz]] and [[fayalite]] at atmospheric pressure unless stabilized by magnesium or other impurities.<ref>{{cite journal |last1=Bohlen |first1=Steven R. |last2=Essene |first2=Eric J. |last3=Boettcher |first3=A.L. |title=Reinvestigation and application of olivine-quartz-orthopyroxene barometry |journal=Earth and Planetary Science Letters |date=March 1980 |volume=47 |issue=1 |pages=1–10 |doi=10.1016/0012-821X(80)90098-9|bibcode=1980E&PSL..47....1B |hdl=2027.42/23295 |hdl-access=free }}</ref>

Distinctly developed [[crystal]]s are rare, the mineral being usually found as foliated masses embedded in the igneous rocks [[norite]] and hypersthene-[[andesite]], of which it forms an essential constituent.<ref name=EB1911/> The coarse-grained [[labradorite]]-hypersthene-rock (norite) of [[Paul's Island]] off the coast of [[Labrador]] has furnished the most typical material; for this reason, the mineral has been known as Labrador [[hornblende]] or paulite.<ref name=EB1911/>

Color is often gray, brown, or green, and the [[Lustre (mineralogy)|luster]] is usually vitreous to pearly. The [[pleochroism]] is strong, the [[Mohs hardness|hardness]] is 5–6, and the [[specific gravity]] is 3.4–3.9. On certain surfaces it displays a brilliant copper-red metallic sheen, or schiller, which has the same origin as the bronzy sheen of [[bronzite]], but is even more pronounced. Like bronzite, it is sometimes cut and polished as a [[gemstone]].<ref name=EB1911/>

The name "hypersthene" comes from the [[Greek language|Greek]] and means "over strength", and is an allusion to its being harder than the [[amphibole]] mineral [[hornblende]] (a mineral with which it is often confused.<ref>{{cite web |url=http://www.classicgems.net/gem_hypersthene.htm |title=Hypersthene |publisher=ClassicGems.net}}</ref>

Hypersthene has been discredited by the [[International Mineralogical Association]] and is no longer considered a valid mineral type; specimens labelled as hypersthere are usually ferroan enstatite.<ref>{{cite web |title=Hypersthene |url=https://www.mindat.org/min-1995.html |publisher=mindat |access-date=1 May 2025}}</ref>

==References==
{{Reflist}}
{{Refbegin}}
*[https://web.archive.org/web/20051029161233/http://mineral.galleries.com/minerals/silicate/hypersth/hypersth.htm Mineral galleries]
*[http://webmineral.com/data/Hypersthene.shtml Webmineral]
*[http://www.mindat.org/show.php?id=1995&ld=1&pho= Mindat locations]
*[http://www.minerals.net/mineral/silicate/ino/pyroxene/enstatit/enstatit.htm= Enstatite-Hypersthene-Ferrosillite series]
{{Refend}}
{{Authority control}}

[[Category:Magnesium minerals]]
[[Category:Iron(II) minerals]]
[[Category:Inosilicates]]
[[Category:Orthorhombic minerals]]