Formula: Na4Al3Si9O24Cl
Tectosilicate (framework silicate), scapolite group, forms a series with meionite
Specific gravity: 2.5 to 2.62
Hardness: 5½ to 6
Streak: White
Colour: Colourless, white, bluish, brownish, yellowish, violet, greenish
Common impurities: Fe,Ca,K,S

Volcanic igneous environments
Metamorphic environments
Hydrothermal environments

Marialite typically occurs in regionally metamorphosed rocks, especially marble, calcareous gneiss, granulite and greenschist. It also occurs in skarn, some pegmatites, pneumatolytically or hydrothermally altered mafic igneous rocks and ejected volcanic blocks. Associated minerals include plagioclase, garnet, pyroxenes, amphiboles, apatite, titanite and zircon (HOM, Mindat).


The Purple Diopside Mound, Rose Road, Pitcairn, St. Lawrence county, New York, USA, is situated in marble. The development of veins of large crystals probably occurred as a result of fluid penetration from a concurrent intrusion. Many of the minerals of interest to collectors formed during this primary event, with additional species resulting from the subsequent alteration of scapolite. There seems to be little, if any, secondary, late-stage mineralisation present.
Marialite occurs as white outer zones on grey meionite crystals (R&M 90.5.446, R&M 96.6.550).

At the Selleck Road Tremolite and Tourmaline Locality, West Pierrepont, St. Lawrence County, New York, USA, marialite occurs as prismatic crystals to 10 cm in complex clusters to 20 cm. Most crystals are altered to creamy white microcline, at least on their surfaces, and many have been completely replaced by that mineral. Unaltered marialite is most common in the Walter-Crump pit, the Walter-Wallace pit, and the Carlin trench.
At the Walter-Crump pit, tremolite crystals, large diopside crystals, some altered to, and overgrown by, tremolite, and quartz crystals formed along the contacts a series of convoluted contacts between marble and tremolite-diopside rock. Locally masses of lavender marialite were encountered in groups of interlocking crystals, mostly altered to microcline except in the centres.
At the Walter-Wallace pit significant specimens of lavender marialite crystals, often partially replaced by creamy white microcline, were recovered from a large pocket of fluor-uvite crystals.
At the Carlin trench marialite was found in a vein that also contained phlogopite triplet twins, albite, microcline, heulandite-Ca, and fluor-uvite (R&M 91-2.123).

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