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The Mineral meionite

Giant Meionite Crystals

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)

Color

White, gray, colorless, cream, yellow, bluish-gray, and purple. Less commonly blue, brown, green, red, and pink.

Crystal System

Tetragonal

Properties

Streak
White
Hardness
5 - 6
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.

Crystal Habits

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.

3D Crystal Atlas

Additional Information

Composition
Calcium aluminum carbonate-silicate
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

Noteworthy Localities

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.

Distingushing Similar Minerals

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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