View source for Rhodonite

{{short description|Single chain manganese inosilicate (MnSiO<sub>3</sub>)}}
{{infobox mineral
| name        = Rhodonite
| category    = [[Inosilicate]]
| image       = 8224M-rhodonite3.jpg
| boxbgcolor  = pink
| boxtextcolor = black
| caption     = Rhodonite from San Martín Mine, Chiurucu, Huallanca District, Bolognesi Province, [[Ancash]], [[Peru]]<br>Specimen size: {{cvt|53|×|52|×|40|mm}}
| formula     = (Mn<sup>2+</sup>, Fe<sup>2+</sup>, Mg, Ca)SiO<sub>3</sub>
| IMAsymbol   = Rdn<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.DK.05
| dana        = 65.04.01.01
| system      = [[Triclinic]]
| class       = Pinacoidal ({{overline|1}}) <br/><small>(same [[H–M symbol]])</small>
| symmetry    = ''P''{{overline|1}}
| unit cell   = {{nobr|1=''a'' = 9.758 [[angstrom|Å]]}}, {{nobr|1=''b'' = 10.499 Å}}, {{nobr|1=''c'' = 12.205 Å}}; {{nobr|1=α = 108.58°}}, {{nobr|1=β = 102.92°}}, {{nobr|1=γ = 82.52°}}; {{nobr|1=Z = 20}}
| color       = Pink, rose-pink to brownish red, red, gray and yellow
| colour      = 
| habit       = Tabular crystals, massive, granular
| twinning    = Lamellar, composition plane {010}
| cleavage    = Perfect on {110} and {1{{overline|1}}0}, (110) ^ (1{{overline|1}}0) = 92.5°; good on {001}
| fracture    = Conchoidal to uneven
| tenacity    = 
| mohs        = 5.5–6.5
| luster      = Vitreous to pearly
| streak      = White
| diaphaneity = Transparent to translucent
| gravity     = 3.57–3.76
| density     = 
| polish      = 
| opticalprop = Biaxial (+)
| refractive  = {{nobr|1=''n''<sub>α</sub> = 1.711–1.738}}, {{nobr|1=''n''<sub>β</sub> = 1.714–1.741}}, {{nobr|1=''n''<sub>γ</sub> = 1.724–1.751}}
| birefringence = ''δ'' = 0.013
| pleochroism = Weak
| 2V          = 58° to 73° (measured), 58° (calculated)
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = 
| alteration  = Exterior commonly black from manganese oxides
| references  = <ref name=Handbook>''[http://rruff.geo.arizona.edu/doclib/hom/rhodonite.pdf Handbook of Mineralogy]''.</ref><ref name=Mindat>[http://www.mindat.org/min-3407.html Rhodonite], Mindat.org.</ref><ref name=Webmin>[http://webmineral.com/data/Rhodonite.shtml Rhodonite], Webmineral data.</ref>
}}

'''Rhodonite''' is a [[manganese]] inosilicate, with the [[chemical formula|formula]] (Mn, Fe, Mg, Ca)SiO<sub>3</sub>, and member of the [[pyroxenoid]] group of [[mineral]]s, crystallizing in the [[triclinic]] system. It commonly occurs as cleavable to compact masses with a [[rose (color)|rose-red color]] (its name comes {{etymology|grc|''{{wikt-lang|grc|ῥόδον}}'' ({{grc-transl|ῥόδον}})|rose}}), often tending to brown due to surface [[redox|oxidation]]. The rose-red hue is caused by the manganese [[cation]] (Mn{{sup|2+}}).<ref>{{cite web |title=Minerals Colored by Metal Ions |url=http://minerals.gps.caltech.edu/color_causes/Metal_Ion/index.html |access-date=2023-02-28 |website=minerals.gps.caltech.edu}}</ref>

Rhodonite [[crystal]]s often have a thick tabular [[crystal habit|habit]], but are rare. It has a perfect, prismatic [[Cleavage (crystal)|cleavage]], almost at right angles. The [[Mohs scale of mineral hardness|hardness]] is 5.5–6.5, and the [[specific gravity]] is 3.4–3.7; [[lustre (mineralogy)|luster]] is vitreous, being less frequently pearly on cleavage surfaces. The manganese is often partly replaced by [[iron]], [[magnesium]], [[calcium]], and sometimes [[zinc]], which may sometimes be present in considerable amounts; a greyish-brown variety containing as much as 20% of calcium oxide is called ''[[bustamite]]''; ''fowlerite'' is a zinciferous variety containing 7% of zinc oxide.
[[File:rhodonite09.jpg|thumb|left|Pink rhodonite contrasting with black manganese oxides is sometimes used as [[gemstone]] material as seen in this specimen from [[Humboldt County, Nevada|Humboldt County]], [[Nevada]].]]
The [[silicate minerals|inosilicate]] (chain silicate) structure of rhodonite has a repeat unit of five silica [[tetrahedra]]. The rare [[Polymorphism (materials science)|polymorph]] ''[[pyroxmangite]]'', formed at different conditions of pressure and temperature, has the same chemical composition but a repeat unit of seven tetrahedra.

Rhodonite has also been worked as an ornamental stone. In the iron and manganese mines at Pajsberg near [[Filipstad]] and [[Långban]] in [[Värmland]], [[Sweden]], small brilliant and translucent crystals (pajsbergite) and cleavage masses occur. Fowlerite occurs as large, rough crystals, somewhat resembling pink [[feldspar]], with [[franklinite]] and zinc ores in granular [[limestone]] at [[Franklin Furnace]] in [[New Jersey]].

Rhodonite is the official [[gemstone]] of the [[List of Massachusetts state symbols|Commonwealth of Massachusetts]].<ref>[http://www.mass.gov/legis/laws/mgl/2-15.htm General Laws of Massachusetts, Chapter 2, Section 15] {{Webarchive|url=https://web.archive.org/web/20081123054240/http://www.mass.gov/legis/laws/mgl/2-15.htm |date=2008-11-23 }}.</ref>
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==See also==
* [[Enstatite]], with MgSiO<sub>3</sub> and FeSiO<sub>3</sub> end-members
* [[Khondalite]]
* [[Wollastonite]], CaSiO<sub>3</sub>

==References==
{{reflist}}
{{EB1911|wstitle=Rhodonite}}
{{Commons category|position=left}}

{{Manganese minerals}}
{{Gemstones}}

[[Category:Gemstones]]
[[Category:Manganese(II) minerals]]
[[Category:Iron(II) minerals]]
[[Category:Magnesium minerals]]
[[Category:Calcium minerals]]
[[Category:Pyroxene group]]
[[Category:Triclinic minerals]]
[[Category:Minerals in space group 2]]