Serandite
Serandite from Mont Saint-Hilaire, Quebec, Canada
General
CategoryInosilicates
Formula
(repeating unit)		Na(Mn2+,Ca)2Si3O8(OH)
IMA symbolSrd[1]
Strunz classification9.DG.05
Dana classification65.2.1.5
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 7.683(1) Å, b = 6.889(1) Å
c = 6.747(1) Å, α = 90.53(5)°
β = 94.12(2)°, γ = 102.75(2)°
Z = 2
Identification
Coloursalmon pink to orange
TwinningAround [010] composition plane {100}, less commonly contact twin on {110}
CleavagePerfect on {001} and {100}
FractureIrregular, uneven
TenacityBrittle
Mohs scale hardness5 to 5.5
LusterVitreous to greasy; fibrous aggregates are dull to silky[2]
StreakWhite
DiaphaneityTransparent, Translucent
Density3.34 g/cm3 (measured)
Optical propertiesBiaxial (+)
Refractive indexnα = 1.668
nβ = 1.671
nγ = 1.703
Birefringenceδ = 0.035
2V angle39°
Dispersionr < v moderate
References[3]

Serandite[4] is a mineral with formula Na(Mn2+,Ca)2Si3O8(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.[5]

Description

Serandite is transparent to translucent and is normally salmon-pink, light pink, rose-red, orange, brown, black, or colorless; in thin section, it is colorless.[2] Octahedrally bonded Mn(II) is the primary contributor to the mineral's pink colors.[6]

Crystals of the mineral can be prismatic to acicular and elongated along [010], bladed, blocky, or tabular and flattened on {100}, occur as a radiating aggregate, or have massive habit.[2] Sérandite is a member of the wollastonite group and is the manganese analogue of pectolite.[3] It is sometimes used as a gemstone.[7]

History

Serandite was discovered on Rouma Island, part of the Los Islands in Guinea.[3] The mineral was described by À. Lacroix in the journal Comptes rendus hebdomadaires des séances de l'Académie des Sciences.[8] He named it sérandite in honor of J.M. Sérand, a mineral collector who helped in the collection of the mineral.[3]

Occurrence and distribution

Serandite has been found in Australia, Brazil, Canada, Guinea, Italy, Japan, Namibia, Norway, Russia, South Africa, and the United States.[3] The type material is held at the National Museum of Natural History in Washington, D.C.[2]

At Mont Saint-Hilaire, Quebec, serandite occurs in sodalite xenoliths and pegmatites cutting syenites within an intrusive alkalic gabbro-syenite complex. In Point of Rocks, New Mexico, it occurs in vugs in phonolite. At the Tumannoe deposit in Russia, serandite occurs in a manganese rich deposit associated with volcanic rocks and terrigenous (non-marine) sediments which has been altered by contact metamorphism.[2]

Serandite has been found in association with aegirine, analcime, arfvedsonite, astrophyllite, eudialyte, fluorite, leucophanite, mangan-neptunite, microcline, nepheline, sodalite, and villiaumite.[2]

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. 1 2 3 4 5 6 "Sérandite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Archived from the original (PDF) on September 11, 2021. Retrieved July 11, 2012.
  3. 1 2 3 4 5 "Sérandite". Mindat. Retrieved July 11, 2012.
  4. ↑ "Serandite". Webmineral. Retrieved July 25, 2012.
  5. ↑ Hålenius, U., Hatert, F., Pasero, M., and Mills, S.J., IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) Newsletter 28. Mineralogical Magazine 79(7), 1859–1864
  6. ↑ Manning, p. 357.
  7. ↑ Gemstones of North America - Volume 3 - Page 417 John Sinkankas - 1959
  8. ↑ Lacroix, p. 189.

Bibliography

Further reading

Media related to Serandite at Wikimedia Commons

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