Leucite


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Related to Leucite: nepheline, natrolite, analcime

leucite

[′lü‚sīt]
(mineralogy)
KAlSi2O6 A white or gray rock-forming mineral belonging to the feldspathoid group; at ordinary temperatures the mineral exists as aggregates of trapezohedral crystals with glassy fracture; hardness is 5.5-6.0 on Mohs scale, and specific gravity is 2.45-2.50. Also known as amphigene; grenatite; vesuvian; Vesuvian garnet; white garnet.

Leucite

 

a mineral whose chemical composition is K(AlSi2-O6); contains 21.58 percent K2O, 23.40 percent AI2O3, and 55.02 percent SiO2; often has admixtures of Na and Ca. Leucite is an aluminosilicate with a skeletal crystal lattice structure. It crystallizes in the isometric system and usually occurs in round crystals of isometric form. At temperatures below 605°C leucite changes to a tetragonal modification and forms finely twinned paramorphs along the crystals of the isometric leucite. Leucite is white in color with a grayish or yellowish tint. It has a hardness of 5–6 on Moh’s scale; its density is 2,450–2,500 kg/m3. It forms porphyritic phenocrysts in lavas rich in alkalis and low in silica. Leucite is found in lavas (for example, Mount Vesuvius). In the USSR it is found in certain effusive rocks in the Armenian SSR, central Kazakhstan, and Eastern Siberia.

References in periodicals archive ?
The first particle used for filling purposes in dental ceramics is a crystalline mineral called potassium leucite, which is in the form of potassium alumina silicate (6).
The increase in solubility of leucite crystals may be another explanation of this undesired property ot the ceramic core.
Hinds, "Ion-exchange in crystals of analcite and leucite," Journal of the Chemical Society, pp.
[10] Furthermore, repeated firings may also produce changes in micro-crack density and partial decoupling of the leucite from the surrounding glass matrix, resulting in a lowering of the bulk thermal expansion of the porcelain.
Typical minerals found in lamproite rocks include forsterite, leucite, phlogopite, and iron-rich sanidine.
The new wet grinding function of Zenotec select hybrid accommodates the milling requirements of the lithium disilicate glass-ceramic IPS e.max CAD and the leucite glass- ceramic IPS Empress CAD.
Standards included diopside (Ca, Mg), fluorite (F), jadeite (Na, Al), leucite (K), magnetite (Fe), quartz (Si), RbCl (Rb), rhodonite (Mn), rutile (Ti), spinel (Cr) and tugtupite (Cl).
Three commercially available IRCs, which were chosen in accordance with their different types of filler particles; two microhybrids, Gradia (GRD; GC Europe, Leuven, Belgium) and Tescera (TES; Bisco Inc., Schaumburg IL USA), and one hybrid, Estenia C&B (EST; Kuraray Medical Co, Tokyo, Japan); two ceramic materials: a glass ceramic, Empress 2 layering (E2; Ivoclar Vivadent, Schaan, Liechtenstein), and a leucite reinforced glass ceramic, Empress Esthetic (EE; Ivoclar Vivadent, Schaan, Liechtenstein); and two PPPs: Detartrine (DT; Septodont GmbH, Niederkassel Germany) and Topex (TP; Sultan Healthcare, Hackensack NJ, USA), were used in the study.
Exposing materials to temperatures of 1200 [degrees]C led to the transformation of the K-A-S-H gel by structurally reorganizing and subsequently crystallizing leucite (KAlSi2O6)- and kalsilite (KAlSiO4)-type structures for each system under study (PS, RHA, SF).
Exports of Felspar, Nepheline, Nepheline Syenite, Leucite and Fluorspar has grew month on month basis by 348.35%.
The intrusive analogues (theralites, essexitic gabbros, ijolites and essexites) show a holocrystalline inequigranular texture, with diopsidic pyroxene ([Wo.sub.44-51][Fs.sub.8-17]), olivine ([Fo.sub.75-82] to [Fo.sub.44-66]), mica (Ti-phlogopite to Ti-biotite), Timagnetite, alkali feldspar, and nepheline ([Ne.sub.64-80][Ks.sub.20-36]) [+ or -] leucite [+ or -] amphibole.
The PFM veneer was Ceramco 3 (Dentsply Prosthetics, York, PA) (1), a feldspathic veneering porcelain containing about 0.30 volume fraction leucite. The veneer for the zirconia, Ceramco PFZ (Dentsply Prosthetics, York, PA), was designed to be used with a 3 mole % yttria stabilized zirconia (Cercon) made by the same manufacturer.