Leucite

leucite

One of the most common feldspathoid minerals, potassium aluminosilicate (KAlSi₂O₆). It occurs only in igneous rocks, particularly potassium-rich, silica-poor, recent lavas. Some important localities include Rome, Italy; Uganda; and Wyoming's Leucite Hills. Leucite is used as a fertilizer in Italy (because of its high potassium content) and as a source of commercial alum.

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leucite [′lü‚sīt]

(mineralogy)

KAlSi₂O₆A 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.

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Leucite 

a mineral whose chemical composition is K(AlSi_2-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.