Sudoite
General
CategoryChlorite_group
Formula
(repeating unit)		Mg2Al3(Si3Al)O10)(OH)8
Crystal systemMonoclinic
Identification
ColorWhite to light green
Mohs scale hardness2.5–3.5
Lusterpearly, dull
Refractive indexnα = 1.581 à 1.583
nβ = 1.584 à 1.589
nγ = 1.591 à 1.601
Birefringencebiaxial (-) ; δ = 0.010 to 0.018
2V = 64 to 70° (measured)
2V = 68 to 72° (calculated)
References.[1][2]

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.[3] The mineral tosudite also wears his name. It was approved as a valid species by the International Mineralogical Association in 1966.

Caracteristics

Sudoite is a clay mineral with chemical formula defined as Mg2Al3(Si3Al)O10)(OH)8. it has a monoclinic crystal system. Its hardness on the Mohs scale is comprised between 2.5 and 3.5.

Classification

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

Members of the 9.EC.55 group
Mineral Formula Symmetry group Space group
Baileychlore(Zn,Al)
3[Fe
2Al][Si
3AlO
10](OH)
8		1 or 1C1 or C1
BorocookeiteLi
1+3xAl
4-x(BSi
3)O
10(OH,F)
8 (x ≤ 0,33)		2/mC2/m
Chamosite(Fe,Mg,Fe)
5Al(Si
3Al)O
10(OH,O)
8		2/mC2/m
Clinochlore(Mg,Fe)
5Al(Si
3Al)O
10(OH)
8		2/mC2/m
CookeiteLiAl
4(Si
3Al)O
10(OH)
8		1, 2 or 2/mC1, C2 or Cc
DonbassiteAl
2[Al
2,33][Si
3AlO
10](OH)
8		2/mC2/m
FranklinfurnaceiteCa(Fe,Al)Mn
4Zn
2Si
2O
10(OH)
8		2C2
GlagoleviteNaMg
6[Si
3AlO
10](OH,O)
8·H
2O		1C1
GonyeriteMn
3[Mn
3Fe][(Si,Fe)
4O
10](OH,O)
8		unknown
Nimite(Ni,Mg,Fe)
5Al(Si
3Al)O
10(OH)
8		2/mC2/m
Odinite(Fe,Mg,Al,Fe,Ti,Mn)
2,5(Si,Al)
2O
5(OH)
4		mCm
Orthochamosite(Fe,Mg,Fe)
5Al(Si
3Al)O
10(OH,O)
8		unknown
PennantiteMn
5Al(Si
3Al)O
10(OH)
8		2/mC2/m
SudoiteMg
2(Al,Fe)
3Si
3AlO
10(OH)
8		2/mC2/m

Formation

It has been first discovered in the Knollenberg Keuper formation, in the village of Plochingen, Stuttgart Region (Baden-Württemberg, Germany).[4] 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[5][6][7]

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.[8] The precise source of such formation of sudoite allowing to carve artifacts in rather large blocks remain unknown.

References

  1. ↑ Sudoite mineral information and data Mindat
  2. ↑ Sudoite Mineral Data Webmineral
  3. ↑ Kohyama, Norihiko (2000). "In memory of Prof. Toshio Sudo". Clay Science. 11 (2): 103–105. doi:10.11362/jcssjclayscience1960.11.103.
  4. ↑ v. Engelhardt, W.; Müller, Germ; Kromer, H. (1962). "Dioktaedrischer Chlorit ("Sudoit") in Sedimenten des Mittleren Keupers von Plochingen (Württ.)". Naturwissenschaften. 49 (9): 205–206. Bibcode:1962NW.....49..205V. doi:10.1007/BF00633957. ISSN 1432-1904. S2CID 21590699.
  5. ↑ Fransolet, André-Mathieu; Bourguignon, P. (1978). "Di/trioctahedral chlorite in quartz veins from the Ardenne, Belgium". The Canadian Mineralogist. 16 (3): 365–373.
  6. ↑ Goffé, Bruno; Michard, André; Kienast, Jean Robert; Le Mer, Olivier (1988). "A case of obduction-related high-pressure, low-temperature metamorphism in upper crustal nappes, Arabian continental margin, Oman: P-T paths and kinematic interpretation". Tectonophysics. The Ophiolites of Man. 151 (1): 363–386. Bibcode:1988Tectp.151..363G. doi:10.1016/0040-1951(88)90253-3. ISSN 0040-1951.
  7. ↑ Ruiz Cruz, María Dolores; de Galdeano, Carlos Sanz (2005). "Compositional and structural variation of sudoite from the Betic Cordillera (Spain): a TEM/AEM study". Clays and Clay Minerals. 53 (6): 639–652. Bibcode:2005CCM....53..639C. doi:10.1346/CCMN.2005.0530610. hdl:10261/18786. S2CID 52107572. Retrieved 2018-10-20.
  8. ↑ Queffelec, Alain; Bellot-Gurlet, Ludovic; Foy, Eddy; Lefrais, Yannick; Fritsch, Emmanuel (2021). "First identification of sudoite in the Caribbean Ceramic Age lapidary craftsmanship". Gems and Gemology. 57 (3): 206–226. doi:10.5741/GEMS.57.3.206. S2CID 245282849.


attribution translated from fr:Sudoïte

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