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Marialite - Wikipedia

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Sodium endmember in the scapolite group of tectosilicate minerals

Marialite Category Tectosilicate minerals, scapolite group Formula Na4Al3Si9O24Cl IMA symbol Mar[1] Strunz classification 9.FB.15 Crystal system Tetragonal Crystal class Dipyramidal (4/m)
(same H-M symbol) Space group I4/m Unit cell a = 12.06 Å, c = 7.572(3) Å; Z = 2 Color Colorless, white, grey; pink, violet, blue, yellow, brown, orange-brown, pale green or reddish Crystal habit Typically flat, pyramidal striated crystals; massive, granular Cleavage Distinct on {100} and {110} Fracture Uneven to conchoidal Tenacity Brittle Mohs scale hardness 5+1⁄2–6 Luster Vitreous, pearly, resinous Streak White Diaphaneity Transparent to opaque Specific gravity 2.55–2.74 Density 2.5–2.62 g/cm3 Optical properties Uniaxial (−) Refractive index nω = 1.539–1.550 nε = 1.532–1.541 Birefringence δ = 0.007 – 0.009 References [2][3][4][5][6]

Marialite is a silicate mineral with a chemical formula of Na4Al3Si9O24Cl[5][6] if a pure endmember or Na4(AlSi3O8)3(Cl2,CO3,SO4) with increasing meionite content. Marialite is the sodium endmember of the scapolite group and a solid solution exists between marialite and meionite, the calcium endmember.[3] It is a rare mineral usually used as a collector's stone.

Marialite has tetragonal crystallography and a 4/m crystal class. It has a 4 fold rotation with 90° mirror planes. Crystals are usually prismatic with prominent forms of prisms and dipyramids.[7]

Marialite belongs to a uniaxial negative optical class which means it has one circular section and a principal section shaped like an oblate sphenoid.

Discovery and occurrence[edit]

Marialite was first described in 1866 for an occurrence in the Phlegrean Volcanic complex, Campania, Italy. It was named by German mineralogist Gerhard vom Rath for his wife, Maria Rosa vom Rath.[4][5]

Marialite occurs in regional and contact metamorphism: marble, calcareous gneiss, granulite and greenschist. It also occurs in skarn, pegmatite and hydrothermally altered volcanic rocks.[4][5] This means that Marialite is formed in high pressure and/or high temperature environments.

  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. ^ Mineralienatlas
  3. ^ a b Klein, C., and Dutrow, B. (2007) The 23rd Edition of the Manual of Mineral Science, 675 p. John Wiley and Sons, Inc. Hoboken, New Jersey, U.S.A.
  4. ^ a b c Handbook of Mineralogy
  5. ^ a b c d Mindat.org
  6. ^ a b Webmineral data
  7. ^ Johnsen, O. (2000) Photographic Guide to Minerals of the World. 439 p. Oxford University Press, Great Clarendon Street, Oxford

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