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Giant Meionite Crystals

The Mineral meionite

Meionite is the calcium-rich end member of the Scapolite series. It is very similar and often indistinguishable from Marialite, the other end member of the series. Intermediary forms of Meionite and Marialite are frequent, and these are classified simply as Scapolite. Of the two Scapolite minerals, Meionite is the more prevalent form. Meionite is named for the Greek word meion (μειον), which translates as "minus", in reference to its lesser termination angles when compared to Vesuvianite.
Chemical Formula Ca4(Al6Si9O24)(CO3)
Composition Calcium aluminum carbonate-silicate
Variable Formula (Ca,Na)4(Al,Si)3Si6O24)(CO3,Cl,SO4)
Color White, gray, colorless, cream, yellow, bluish-gray, and purple. Less commonly blue, brown, green, red, and pink.
Streak White
Hardness 5 - 6
Crystal System Tetragonal
3D Crystal Atlas
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Crystal Forms
and Aggregates
Crystals are often short and stout with a slightly angled or pyramidal termination, or long and prismatic. Crystals can be very large and fat, and are often intergrown in groups of such crystals or are columnar. Also grainy, massive, and crudely as formed crystal masses. Prismatic crystals are often striated.
Transparency Transparent to opaque
Specific Gravity 2.6 - 2.8
Luster Vitreous to dull
Cleavage 2,2
Fracture Conchoidal, uneven
Tenacity Brittle
Other ID Marks Often fluorescent, sometimes brightly. Colors include white, yellow, and pink. Fluorescence may be present both in shortwave and longwave.
In Group Silicates; Tectosilicates
Striking Features Crystal habit, environment, and fluorescence
Environment Chiefly in metamorphic rocks, in metamorphosed limestones, skarns, gneisses, and hornfels. Also in granite pegmatites.
Rock Type Igneous, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 1
Demand (1-3) 2


The two Scapolite members often occur together and are not usually individually distinguished. See Scapolite for a comprehensive list of localities general to the Scapolite series.

Diopside, Biotite, Phlogopite, Titanite, Hornblende, Actinolite, Almandine, Microcline, Muscovite

Meionite - Difficult to distinguish without chemical analysis.
Feldspars - Often form in different crystal habits, lacks fluorescence.
Nepheline - Different cleavage, lacks fluorescence.

meionite PHOTOS
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