Ramsdellite

{{Short description|Oxide mineral}} {{Infobox mineral | name = Ramsdellite | image = Ramsdellite-ram-05a.jpg | alt = | caption = Sample from Mistake Mine, Box Canyon District, Yavapai County, Arizona, USA | category = Oxide minerals | formula = {{Chem2|MnO2}} | IMAsymbol = Rmd<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |s2cid=235729616 |doi-access=free|url-access=subscription}}</ref> | molweight = 86.94 gm (Mn 63.19% O 36.81%) | strunz = 04.DB.15a | dana = 04.04.07.01 | system = Orthorhombic | class = Dipyramidal | symmetry = ''Pbnm'' (no. 62) | unit cell = | color = Iron black, Black, Steel gray | habit = Granular / Massive-Fibrous / Platy | twinning = | cleavage = Good | fracture = Conchoidal to uneven{{sfn|The Mineral Ramsdellite – galleries}} | tenacity = Brittle | mohs = 3 – Calcite | luster = Metallic | streak = Brownish black | diaphaneity = Opaque | gravity = 4.79 g/cm³ (calculated) | density = 4.37 g/cm³ (measured) | polish = | opticalprop = NCalc= 2.89 (Dcalc) / 2.72 (Dmeas) | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | Curie temp = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = {{sfn|Ramsdellite Mineral Data}} }} '''Ramsdellite''' (Mn⁴⁺O₂) is an orthorhombic manganese dioxide mineral. It is relatively uncommon, and is usually found in deposits containing other manganese oxide crystals.

==Name==

Ramsdellite is named after the American mineralogist, Lewis Stephen Ramsdell (1895–1975).{{sfn|Ramsdellite Mineral Data}} Ramsdell spent almost all his career at the University of Michigan as a professional mineralogist. Ramsdellite was one of the new phases he first recognized in the "black manganese oxide" minerals. It was later named in his honour by Michael Fleischer and W. E. Richmond, who fully described the mineral in 1943.{{sfn|Willett F. Ramsdell – U of Michigan}} The mineral is also called Groutellite.{{sfn|Ramsdellite – mindat.org}}

==Chemistry and crystallography==

The chemical formula for Ramsdellite is MnO₂. The empirical formula is Mn⁴⁺O₂.{{sfn|Ramsdellite Mineral Data}} Ramsdellite has the same chemistry as the more common pyrolusite, but is orthorhombic where pyrolusite is tetragonal.{{sfn|The Mineral Ramsdellite – galleries}} Ramsdellite belongs to the Orthorhombic crystal system and Dipyramidal crystal class.{{sfn|Ramsdellite – mindat.org}} Properties:{{sfn|Ramsdellite – Mineral Data Publishing}} {|class=wikitable |- |rowspan=4|Crystal || System || Orthorhombic |- | Point group || 2/m 2/m 2/m |- |Form ||Often pseudomorphs of groutite crystals |- |Crystal habit || Platy, fibrous or massive |- |rowspan=4|Physical || Cleavage || Prominent, on three pinacoids and a prism |- |Tenacity || Brittle |- |Hardness (Mohs scale) || About 3 |- |D || Measured = 4.65–4.83 Calculated = 4.84 |- |rowspan=7|Optical|| Opaque || |- |Color || Steel-gray to iron-black; yellowish white in reflected light. |- | Streak || Black, may have brownish tint |- | Luster || Brilliant metallic. |- | Optical Class || Biaxial |- | Anisotropism || Strong; pale yellow |- | Bireflectance || Distinct. |- | Cell || Space group || Pbnm. a = 4.533(5) b = 9.27(1) c = 2.866(5) Z = 4 |}

==Classification==

The Dana classification is 4.4.7.1 (simple oxides: AX₂). The Hey's CIM Ref is 7.18.8 (Oxides and Hydroxides, Oxides of Mn).{{sfn|Ramsdellite – mindat.org}} The Nickel–Strunz classification is 04.DB.15a, since the metal:oxygen ratio is around 1:2 and the mineral has medium-sized cations; chains of edge-sharing octahedra.{{sfn|Ramsdellite Mineral Data}} Other elements in the Ramsdellite / 04.DB.15 group are Paramontroseite: V⁴⁺O₂ (15a), Akhtenskite: ε-Mn⁴⁺O₂ (15b) and Nsutite: (Mn⁴⁺,Mn²⁺)(O,OH)₂ (15c).{{sfn|Nickel-Strunz Oxides Classification – webmineral}}{{sfn|Ramsdellite – mindat.org}}

==Distribution==

Ramsdellite is formed by oxidization of weathered manganese minerals such as manganite, and is often found in deposits containing various other manganese oxides. The mineral is relatively rare. {{sfn|The Mineral Ramsdellite – galleries}} The type locality, the place where Ramsdellite was first identified, is the Lake Valley district in Sierra County, New Mexico, US.{{sfn|Ramsdellite – mindat.org}} Other locations in the USA where well-characterized samples of Ramsdellite have been found are Artillery Mountains, Arizona; Mistake mine, Yavapai County, Arizona; Idarado mine, near Telluride, Colorado; and Monroe-Tener mine, near Chisholm, Minnesota.{{sfn|Ramsdellite – Mineral Data Publishing}}

Good samples have been found in Canada along the East River in Pictou County, Nova Scotia; in Mexico in Los Gavilanes, Baja California; In India in Dongari Buzurg, Bhandara, Maharashtra; in Australia in the Iron Monarch quarry, Iron Knob, South Australia; in Japan in the Otoshibetsu and Tanno mines, Hokkaido; in the Czech Republic at Horní Blatná; in Germany at Bütten-Adenstadt, Lower Saxony and Clara Mine, near Oberwolfach, Black Forest; in Egypt at Gebel To Yu, Yoider, and Um Bogna; and in South Africa at Hotazel, near Kuruman, Northern Cape.{{sfn|Ramsdellite – Mineral Data Publishing}} Ramsdellite is found in the manganese deposits near Moanda, Haut-Ogooué Province, Gabon, mined by the Compagnie minière de l'Ogooué. These deposits were formed by supergene enrichment of Precambrian sediments.{{sfn|National Materials Advisory Board|1981|p=178}}

==Notes== {{notes}}{{reflist|30em}}

{{commons category|Ramsdellite}} ==Sources== {{refbegin}} *{{citation |author=National Materials Advisory Board|title=Manganese Reserves and Resources of the World and Their Industrial Implications: Report |url=https://books.google.com/books?id=3CIrAAAAYAAJ&pg=PA177|accessdate=2017-10-24|year=1981|publisher=National Academies|id=NAP:11507}} *{{citation|ref={{harvid|Nickel-Strunz Oxides Classification – webmineral}} |title=Nickel-Strunz Oxides Classification|work=webmineral.com |url=http://webmineral.com/strunz/strunz.php?class=04&subclass=04.D&group=04.DB#.Wj0HHt-nHIU|accessdate=2017-12-22}} *{{citation|ref={{harvid|Ramsdellite – mindat.org}} |title=Ramsdellite|work=mindat.org|publisher=Hudson Institute of Mineralogy |url=https://www.mindat.org/min-3359.html|accessdate=2017-12-22}} *{{citation|ref={{harvid|Ramsdellite Mineral Data}} |title=Ramsdellite Mineral Data|work=webmineral.com |url=http://webmineral.com/data/Ramsdellite.shtml#.Wjk9eN-nHIV|accessdate=2017-12-19}} *{{citation|ref={{harvid|Ramsdellite – Mineral Data Publishing}} |title=Ramsdellite|publisher=Mineral Data Publishing |url=http://www.handbookofmineralogy.org/pdfs/ramsdellite.pdf|accessdate=2017-12-22}} *{{citation|ref={{harvid|The Mineral Ramsdellite – galleries}} |title=The Mineral Ramsdellite|work=galleries.com |url=http://www.galleries.com/Ramsdellite|access-date=2017-12-19}} *{{citation|ref={{harvid|Willett F. Ramsdell – U of Michigan}} |title=Willett F. Ramsdell |publisher= The University of Michigan |url=https://www.lib.umich.edu/faculty-history/faculty/willett-f-ramsdell/memorial|accessdate=2017-12-22}} {{refend}} {{authority control}}

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Category:Manganese(IV) minerals Category:Oxide minerals Category:Orthorhombic minerals Category:Minerals in space group 62 Category:Minerals described in 1943