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Marialite
Chemical Formula	Na4Al3Si9O24Cl
Species	Silicates
Crystal System	Tetragonal
Mohs Scale	5-6
Specific Gravity	2.55-2.74
Color	Colorless, white, grey; pink, Purple, blue, yellow, brown, orange-brown, pale green or reddish
Streak	White
Luster	Vitreous, Resinous, Pearly
Refractive Index	n = 1.539 - 1.550 n = 1.532 - 1.541
Diaphaneity	Transparent, Translucent
Cleavage	Distinct/GoodDistinct on the and the
Fracture	Irregular/Uneven, Conchoidal
Crystal Habit：Typically flat, pyramidal striated crystals; massive, granular
Geological Setting：Regionally and contact metamorphic rocks, skarns, pegmatites, altered mafic igneous rocks, volcanic ejecta.

Marialite is a silicate mineral with a chemical composition of Na₄Al₃Si₉O₂₄Cl if a pure endmember or Na₄(AlSi₃O₈)₃(Cl₂,CO₃,SO₄) with increasing meionite content. Marialite is a member of the scapolite group and a solid solution exists between marialite and meionite, the calcium endmember. It is a rare mineral usually used as a collector's stone. It has a very rare but attractive gemstones and cat's eye.

Crystallography

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.

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

Discovery and occurrence

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.

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