Sudoite Explained

Sudoite
Category:	Chlorite_group
Formula:	Mg2Al3(Si3Al)O10)(OH)8
Color:	White to light green
System:	Monoclinic
Mohs:	2.5–3.5
Luster:	pearly, dull
Refractive:	nα = 1.581 à 1.583 nβ = 1.584 à 1.589 nγ = 1.591 à 1.601
Birefringence:	biaxial (-) ; 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

scope=col	Mineral	scope=col	Formula	scope=col	Symmetry group	scope=col	Space group
		1 or	C1 or C
	(x ≤ 0,33)	2/m	C2/m
		2/m	C2/m
		2/m	C2/m
		, 2 or 2/m	C, C2 or Cc
		2/m	C2/m
		2	C2
		1	C1
			unknown
		2/m	C2/m
		m	Cm
			unknown
		2/m	C2/m
Sudoite		2/m	C2/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

attribution translated from

Notes and References

1. https://www.mindat.org/min-3820.html Sudoite mineral information and data Mindat
2. http://webmineral.com/data/Sudoite.shtml Sudoite Mineral Data Webmineral
3. 10.11362/jcssjclayscience1960.11.103. 11. 2. 103–105. Kohyama. Norihiko. In memory of Prof. Toshio Sudo. Clay Science. 2000.
4. 10.1007/BF00633957. 1432-1904. 49. 9. 205–206. v. Engelhardt. W.. Müller. Germ. Kromer. H.. Dioktaedrischer Chlorit ("Sudoit") in Sedimenten des Mittleren Keupers von Plochingen (Württ.). Naturwissenschaften. 1962. 1962NW.....49..205V. 21590699.
5. 16. 3. 365–373. Fransolet. André-Mathieu. Bourguignon. P.. Di/trioctahedral chlorite in quartz veins from the Ardenne, Belgium. The Canadian Mineralogist. 1978.
6. 10.1016/0040-1951(88)90253-3. 0040-1951. 151. 1. 363–386. Goffé. Bruno. Michard. André. Kienast. Jean Robert. Le Mer. Olivier. 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. 1988. 1988Tectp.151..363G.
7. 10.1346/CCMN.2005.0530610. 53. 6. 639–652. Ruiz Cruz. María Dolores. de Galdeano. Carlos Sanz. Compositional and structural variation of sudoite from the Betic Cordillera (Spain): a TEM/AEM study. Clays and Clay Minerals. 2018-10-20. 2005. 2005CCM....53..639C. 10261/18786. 52107572. free.
8. 10.5741/GEMS.57.3.206. 57. 3. 206–226. Queffelec. Alain. Bellot-Gurlet. Ludovic. Foy. Eddy. Lefrais. Yannick. Fritsch. Emmanuel. First identification of sudoite in the Caribbean Ceramic Age lapidary craftsmanship. Gems and Gemology. 2021. 245282849. free.