La lazurita es un mineral del grupo de los silicatos, subgrupo tectosilicatos. Químicamente es un aluminosilicato con otros cationes de sodio y calcio, de un color azul intenso de gran belleza. Su nombre deriva de la palabra árabe lazurd que significa "cielo". Un sinónimo usado es pigmento azul ultramar o ultramarina. La lazurita es el componente de color azul que se observa en la gema decorativa denominada lapislázuli, la cual es una roca formada por tres minerales: lazurita, calcita y pirita. A veces se toma erróneamente el nombre de esta roca como sinónimo de lazurita. A menudo ha sido confundido la lazurita con la lazulita o con la azurita, dos minerales que no tienen nada que ver con el primero, sólo se parecen en su color azul. Se distingue bien de la lazulita porque ésta tiene un lustre vítreo muy marcado y de la azurita porque ésta reacciona fuertemente con los ácidos.

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Lazurite is a tectosilicate mineral with sulfate, sulfur and chloride with formula: (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]. It is a feldspathoid and a member of the sodalite group. Lazurite crystallizes in the isometric system although well formed crystals are rare. It is usually massive and forms the bulk of the gemstone lapis lazuli. Lazurite is a deep blue to greenish blue. The colour is due to the presence of S−3 anions. It has a Mohs hardness of 5.0 to 5.5 and a specific gravity of 2.4. It is translucent with a refractive index of 1.50. It is fusible at 3.5 and soluble in HCl. It commonly contains or is associated with grains of pyrite. Lazurite is a product of contact metamorphism of limestone and typically is associated with calcite, pyrite, diopside, humite, forsterite, hauyne and muscovite. Other blue minerals such as the carbonate azurite and the phosphate lazulite may be confused with lazurite, but are easily distinguished with careful examination. Lazurite at one time was used as a synonym for azurite. Lazurite was first described in 1890 for an occurrence in the Sar-e-Sang District, Koksha Valley, Badakhshan Province, Afghanistan. It has been mined for over 6,000 years in the lapis lazuli district of Badakhshan, Afghanistan. It has been used as a pigment in painting and cloth dyeing since at least the sixth or seventh century CE. It is also mined at Lake Baikal in Siberia; Mount Vesuvius; Burma; Canada; and the United States. The name is from the Persian lazward for blue.

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