Melilite


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melilite

[′mel·ə‚līt]
(mineralogy)
A sorosilicate mineral group of complex composition [(Na,Ca)2(Mg,Al)(Si,Al)2O7] crystallizing in the tetragonal system; luster is vitreous to resinous, and color is white, yellow, greenish, reddish, or brown; hardness is 5 on Mohs scale, and specific gravity varies from 2.95 to 3.04.

Melilite

 

a rock-forming mineral of the silicate class; a member of the isomorphous series extending from akermanite to gehlenite. Melilite has the chemical composition (Ca, Na)2(Mg, Al) [(Si, Al)2O7] and contains admixtures of Mn2+ and Fe2+. Its crystal structure is characterized by lattices consisting of alternating groups of twinned tetrahedrons [(Si, Al)2O7] as well as of single tetrahedrons—MgO4 and AlO4. The lattices are linked by Ca or Na atoms surrounded by eight oxygen atoms.

Melilite crystallizes in the tetragonal system. It generally occurs in the form of granular aggregates, individual grains, and continuous cryptocrystalline accumulations; crystals are rare. Melilite has a hardness of 5-5.5 on Mohs’ scale and a density of 2,980-3,066 kg/m3. The luster is vitreous, and the color ranges from white to pale yellow, occasionally to greenish yellow and reddish brown. Melilite is usually found in certain ultrabasic alkaline volcanic rocks in association with olivine, nepheline, pyroxene, biotite, and other minerals. Occasionally it occurs in contact-metasomatic (tactile) limestones.

REFERENCE

Mineraly: Spravochnik, vol. 3, fasc. 1. Moscow, 1972.
References in periodicals archive ?
SEM analyses together with EDX element mapping revealed that particles of PF/CA can be divided generally into three types: spherical homogeneously melted ones--they contain Ca-Mg-Al-silicates: melilite [(Ca,Na).
There are also phases like melilite, periclase, belite, merwinite, formed by partial thermal decomposition and subsequent reactions of the initial minerals.
The main glassy component of the "Kivioli spherules" falls within the compositional range of melilites, more precisely K-rich- Na-poor- melilites (see Table).
Many compounds that have been detected in the power plant ash were missing after ash has been stored on ash fields, for example, such compounds as feldspars, melilites, micas and many other freely soluble and leaching out compounds.