Lapis lazuli, also known as lapis lazuli or lapis for short, is a naturally occurring, deep blue metamorphic rock which, depending on where it is found, consists of varying proportions of the minerals lazurite, pyrite, calcite and smaller amounts of diopside, sodalite and others.
The word lapis comes from the Latin language and means "stone". Lazuli, genitive of the Medieval Latin word lazulum for "blue", is derived from the Persian لاجورد / lājevard / 'sky blue', like Medieval Latin lazurium and Greek lazoúrion via Arabic lāzaward. Synonyms include Azur d'Acre, azurum ultramarinum, Bleu d'Azur, Lapis lazuli ultramarine, Las(z)urstein, Lazurium, Oltremare, Oriental blue, Outremer lapis, Pierre d'azur, Ultramarine genuine, Ultramar ino/verdadero, Ultramarine natural; also according to Pliny and Theophrast coeruleum scythium.
Lapis lazuli is mainly formed through contact metamorphosis or metasomatic processes in amphibolites, gneiss, marble, peridotites and pyroxenites, among others. In addition to the rocks mentioned, the minerals afghanite, apatite, dolomite, hauyne, nepheline, sulphur, tremolite and others may also be associated.
Formation and locations
The best-known sites are located in the western Hindu Kush, in the province of Badakhshan in Afghanistan. During the Afghan civil war, the control of the Panjshir Valley played an important role as a source of income for the purchase of weapons, in addition to its strategic importance as a supplier of expensive lapis lazuli. The mines at Sar-é Sang in the Kokcha Valley were already in operation in Ancient Egyptian times. The rock was blasted with wood fires: sudden quenching with cold water created cracks so that it could then be tapped out. Today, explosives are used in Badakhshan.
Other important deposits are located in Russia. Here, the best varieties in terms of color come from the Malobystrinskoye deposit on Lake Baikal. The Talskoye and Sljudjanskoye localities in the Baikal region proved to be less productive. The site on the Sljudjanka River was discovered by Erich G. Laxmann in 1784-1785, when he was conducting scientific research on Lake Baikal on behalf of the Tsar's Academy of Sciences. Catherine the Great sent a geological expedition to this region in 1787 to obtain more precise information about usable gemstones and minerals. As a result, samples of lazurite were also brought to St. Petersburg.
Other sites are located in Tajikistan near Lyadzhvar-Dara in the Pamir Mountains (Badakhshan / Shakhdara Range). There are also sites near Ovalle in Chile, in Iran, in the Cascade Canyon of California and at Magnet Cove in Arkansas (USA).