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

Scapolite

Scapolite , is a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate.-Properties:...

 group and a solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

 exists between marialite and meionite

Meionite

Meionite is a silicate mineral belonging to the scapolite group with the formula Ca4Al6Si6O24CO3. Some samples may also contain a sulfate group. It was first discovered in 1801 on Mt Somma, Vesuvius, Italy....

, 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

Campania

Campania is a region in southern Italy. The region has a population of around 5.8 million people, making it the second-most-populous region of Italy; its total area of 13,590 km² makes it the most densely populated region in the country...

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. It was named by German mineralogist Gerhard vom Rath

Gerhard vom Rath

Gerhard vom Rath , was a German mineralogist, born at Duisburg in Prussia.He was educated at Cologne, at Bonn University, and finally at Berlin, where he graduated Ph.D. in 1853. In 1856 he became assistant to Johann Jakob Nöggerath in the mineralogical museum at Bonn, and succeeded to the...

 for his wife, Maria Rosa vom Rath.

Marialite occurs in regional and contact metamorphism

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

: marble

Marble

Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

, calcareous gneiss

Gneiss

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...

, granulite

Granulite

Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...

 and greenschist

Greenschist

Greenschist is a general field petrologic term applied to metamorphic or altered mafic volcanic rock. The term greenstone is sometimes used to refer to greenschist but can refer to other rock types too. The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the...

. It also occurs in skarn

Skarn

Skarn is an old Swedish mining term originally used to describe a type of silicate gangue, or waste rock, associated with iron-ore bearing sulfide deposits apparently replacing Archean age limestones in Sweden's Persberg mining district. In modern usage the term "skarn" has been expanded to refer...

, pegmatite

Pegmatite

A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....

 and hydrothermally altered volcanic rock

Volcanic rock

Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

s. This means that Marialite is formed in high pressure and/or high temperature environments.