{{Short description|Mineral of the chlorite group}} {{Infobox mineral | name = Sudoite | category = Phyllosilicate minerals | group = Chlorite group | image = | imagesize = | caption = | formula = Mg<sub>2</sub>Al<sub>3</sub>(Si<sub>3</sub>Al)O<sub>10</sub>(OH)<sub>8</sub> | molweight = | color = White to light green | habit = | system = Monoclinic | twinning = | cleavage = | fracture = | mohs = 2.5–3.5 | luster = pearly, dull | refractive = ''n''<sub>α</sub> = 1.581 à 1.583<br>''n''<sub>β</sub> = 1.584 à 1.589<br>''n''<sub>γ</sub> = 1.591 à 1.601 | opticalprop = | birefringence = biaxial (-) ; δ = 0.010 to 0.018<br>2V = 64 to 70° (measured)<br>2V = 68 to 72° (calculated) | pleochroism = | streak = | gravity = | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = | other = |references =<ref>[https://www.mindat.org/min-3820.html Sudoite mineral information and data Mindat]</ref><ref>[http://webmineral.com/data/Sudoite.shtml Sudoite Mineral Data Webmineral]</ref> }}

'''Sudoite''' is a mineral from the chlorite group. It was named after Toshio Sudo (1911–2000), professor of mineralogy at the University of Tokyo, in Japan, and a pioneer of clay science.<ref>{{Cite journal| doi = 10.11362/jcssjclayscience1960.11.103| volume = 11| issue = 2| pages = 103–105| last = Kohyama| first = Norihiko| title = In memory of Prof. Toshio Sudo| journal = Clay Science| date = 2000}}</ref> The mineral tosudite also bears his name. It was approved as a valid species by the International Mineralogical Association in 1966.

== Characteristics == Sudoite is a clay mineral with chemical formula defined as Mg<sub>2</sub>Al<sub>3</sub>(Si<sub>3</sub>Al)O<sub>10</sub>(OH)<sub>8</sub>. It has a monoclinic crystal system. Its hardness on the Mohs scale is between 2.5 and 3.5.

==Classification== Following the Nickel–Strunz classification, it is contained in the "09.EC.55" group:

{| class="wikitable" style="text-align:center;" |+ Members of the 9.EC.55 group |- ! scope=col | Mineral ! scope=col | Formula ! scope=col | Symmetry group ! scope=col | Space group |- | Baileychlore || {{chem|(Zn,Al)|3|[Fe|2|Al][Si|3|AlO|10|](OH)|8}} || 1 or {{overline|1}} || ''C''1 or ''C''{{overline|1}} |- | Borocookeite || {{chem|Li|1+3x|Al|4-x|(BSi|3|)O|10|(OH,F)|8}} (x ≤ 0,33) || 2/''m'' || ''C''2/''m'' |- | Chamosite || {{chem|(Fe,Mg,Fe)|5|Al(Si|3|Al)O|10|(OH,O)|8}} || 2/''m'' || ''C''2/''m'' |- | Clinochlore || {{chem|(Mg,Fe)|5|Al(Si|3|Al)O|10|(OH)|8}} || 2/''m'' || ''C''2/''m'' |- | Cookeite || {{chem|LiAl|4|(Si|3|Al)O|10|(OH)|8}} || {{overline|1}}, 2 or 2/''m'' || ''C''{{overline|1}}, ''C2'' or ''Cc'' |- | Donbassite || {{chem|Al|2|[Al|2,33|][Si|3|AlO|10|](OH)|8}} || 2/''m'' || ''C''2/''m'' |- | Franklinfurnaceite || {{chem|Ca(Fe,Al)Mn|4|Zn|2|Si|2|O|10|(OH)|8}} || 2 || ''C''2 |- | Glagolevite || {{chem|NaMg|6|[Si|3|AlO|10|](OH,O)|8|·H|2|O}} || 1 || ''C''1 |- | Gonyerite || {{chem|Mn|3|[Mn|3|Fe][(Si,Fe)|4|O|10|](OH,O)|8}} || || unknown |- | Nimite || {{chem|(Ni,Mg,Fe)|5|Al(Si|3|Al)O|10|(OH)|8}} || 2/''m'' || ''C''2/''m'' |- | Odinite || {{chem|(Fe,Mg,Al,Fe,Ti,Mn)|2,5|(Si,Al)|2|O|5|(OH)|4}} || ''m'' || ''Cm'' |- | Orthochamosite || {{chem|(Fe,Mg,Fe)|5|Al(Si|3|Al)O|10|(OH,O)|8}} || || unknown |- | Pennantite || {{chem|Mn|5|Al(Si|3|Al)O|10|(OH)|8}} || 2/''m'' || ''C''2/''m'' |- | '''Sudoite''' || {{chem|Mg|2|(Al,Fe)|3|Si|3|AlO|10|(OH)|8}} || 2/''m'' || ''C''2/''m'' |}

== Formation == It has been first discovered in the Knollenberg Keuper formation, in the village of Plochingen, Stuttgart Region (Baden-Württemberg, Germany).<ref>{{Cite journal| doi = 10.1007/BF00633957| issn = 1432-1904| volume = 49| issue = 9| pages = 205–206| last1 = v. Engelhardt| first1 = W.| last2 = Müller| first2 = Germ| last3 = Kromer| first3 = H.| title = Dioktaedrischer Chlorit ("Sudoit") in Sedimenten des Mittleren Keupers von Plochingen (Württ.)| journal = Naturwissenschaften| date = 1962| bibcode = 1962NW.....49..205V| s2cid = 21590699}}</ref> Despite being an unlikely mineral, it has been described in every continent but Antarctica and Oceania. It is found mainly in hydrothermal or high-pressure/low-temperature (HP/LT) metamorphism contexts<ref>{{Cite journal| volume = 16| issue = 3| pages = 365–373| last1 = Fransolet| first1 = André-Mathieu| last2 = Bourguignon| first2 = P.| title = Di/trioctahedral chlorite in quartz veins from the Ardenne, Belgium| journal = The Canadian Mineralogist| date = 1978}}</ref><ref>{{Cite journal| doi = 10.1016/0040-1951(88)90253-3| issn = 0040-1951| volume = 151| issue = 1| pages = 363–386| last1 = Goffé| first1 = Bruno| last2 = Michard| first2 = André| last3 = Kienast| first3 = Jean Robert| last4 = Le Mer| first4 = Olivier| title = A case of obduction-related high-pressure, low-temperature metamorphism in upper crustal nappes, Arabian continental margin, Oman: P-T paths and kinematic interpretation| journal = Tectonophysics| series = The Ophiolites of Man| date = 1988| bibcode = 1988Tectp.151..363G}}</ref><ref>{{Cite journal| doi = 10.1346/CCMN.2005.0530610| volume = 53| issue = 6| pages = 639–652| last1 = Ruiz Cruz| first1 = María Dolores| last2 = de Galdeano| first2 = Carlos Sanz| title = Compositional and structural variation of sudoite from the Betic Cordillera (Spain): a TEM/AEM study| journal = Clays and Clay Minerals| accessdate = 2018-10-20| date = 2005| bibcode = 2005CCM....53..639C| hdl = 10261/18786| s2cid = 52107572| url = http://openurl.ingenta.com/content/xref?genre=article&issn=0009-8604&volume=53&issue=6&spage=639| hdl-access = free}}</ref>

== Use == This mineral has been used as gemstone for the production of personal ornaments, beads and pendants, during the Early Ceramic Age (500 BC – 500 AD), in the Lesser Antilles.<ref>{{Cite journal| doi = 10.5741/GEMS.57.3.206| volume = 57| issue = 3| pages = 206–226| last1 = Queffelec| first1 = Alain| last2 = Bellot-Gurlet| first2 = Ludovic| last3 = Foy| first3 = Eddy| last4 = Lefrais| first4 = Yannick| last5 = Fritsch| first5 = Emmanuel| title = First identification of sudoite in the Caribbean Ceramic Age lapidary craftsmanship| journal = Gems and Gemology| date = 2021| s2cid = 245282849| doi-access = free}}</ref> The precise source of such formation of sudoite allowing to carve artifacts in rather large blocks remain unknown.

== References ==

{{reflist}}

''attribution'' translated from :fr:Sudoïte

Category:Monoclinic crystals Category:Chlorite group