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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. |
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Chemical Formula |
Ca4(Al6Si9O24)(CO3)
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Composition |
Calcium aluminum carbonate-silicate
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| Variable Formula |
(Ca,Na)4(Al,Si)3Si6O24)(CO3,Cl,SO4) |
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Color |
White, gray, colorless, cream, yellow, bluish-gray, and purple. Less commonly blue, brown, green, red, and pink. |
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Streak |
White |
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Hardness |
5 - 6 |
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Crystal System |
Tetragonal |
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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. |
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Transparency |
Transparent to opaque |
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Specific Gravity |
2.6 - 2.8 |
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Luster |
Vitreous to dull |
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Cleavage |
2,2 |
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Fracture |
Conchoidal, uneven |
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Tenacity |
Brittle |
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Other ID Marks |
Often fluorescent, sometimes brightly. Colors include white, yellow, and pink. Fluorescence may be present both in shortwave and longwave. |
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In Group |
Silicates; Tectosilicates |
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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 |
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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1 |
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Demand (1-3) |
2 |
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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.
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Meionite - Difficult to distinguish without chemical analysis.
Feldspars - Often form in different crystal habits, lacks fluorescence.
Nepheline - Different cleavage, lacks fluorescence.
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