Serandite - Misplaced Pages

(Redirected from Sérandite) Mineral

Serandite
Serandite from Mont Saint-Hilaire, Quebec, Canada
General
Category	Inosilicates
Formula (repeating unit)	Na(Mn,Ca)₂Si₃O₈(OH)
IMA symbol	Srd
Strunz classification	9.DG.05
Dana classification	65.2.1.5
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	P1
Unit cell	a = 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
Colour	salmon pink to orange
Twinning	Around composition plane {100}, less commonly contact twin on {110}
Cleavage	Perfect on {001} and {100}
Fracture	Irregular, uneven
Tenacity	Brittle
Mohs scale hardness	5 to 5.5
Luster	Vitreous to greasy; fibrous aggregates are dull to silky
Streak	White
Diaphaneity	Transparent, Translucent
Density	3.34 g/cm (measured)
Optical properties	Biaxial (+)
Refractive index	n_α = 1.668 n_β = 1.671 n_γ = 1.703
Birefringence	δ = 0.035
2V angle	39°
Dispersion	r < v moderate
References

Serandite is a mineral with formula Na(Mn,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.

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. Octahedrally bonded Mn(II) is the primary contributor to the mineral's pink colors.

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

History

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

Occurrence and distribution

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

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.

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

References

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.
^ "Sérandite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Archived from the original (PDF) on September 11, 2021. Retrieved July 11, 2012.
^ "Sérandite". Mindat. Retrieved July 11, 2012.
"Serandite". Webmineral. Retrieved July 25, 2012.
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
Manning, p. 357.
Gemstones of North America – Volume 3 – Page 417 John Sinkankas – 1959
Lacroix, p. 189.