Lazurite

Lazurite

     (Na, Ca)₈[ (SO₄ , S, CL)₂(AlSiO₄)₆ ]
In various references the chemical formula of lazurite varies.
     Usually lazurite there is in continuous mass. Jewelry lazurite is the polymeric thin or fine and the medium-grained corpuscles, in which grains of lazurite closely grow together with calcite (seldom with dolomite), diopside, phlogopite. Frequently there is pyrite. The size of corpuscle - the 100-th - the tenth shares of millimeter, less often some millimeters, their form are isometric or extended, frequently zonal.
     Color: saturated, dark blue, blue, blue-violet, green-dark blue.
     Hardness: 5 - 6 on Мohs scale.
     Density: 2,38-2,9 gr/sm³.
     Break: rough.
     Shine: glass.
     Transparency: opaque.
     Fluorescence: strong, white.
     Coloring of lazurite is bright - dark blue. Its name origin from "lapis lazuli" - Italian term. It concerns to group of sodalite, is genetically connected with silicate-magnesian skarns of ancient metamorphic silicaо-carbonaceous formations.
     Lazurite for millenia B.C. in Ancient Egypt, Mesopotamia, and then in Ancient Greece and Ancient Rome was applied. From lazurite produced a steady dark blue paint - the ultramarine, cut out figurines, various amulets. Valuable natural lazurite paint was used by well-known artists of Renaissance. In Russia in 18 and 19 centuries lazurite was appreciated very highly. Of it made highly artistic gemstone wares and inserts in jewels.
     New epoch of application of lazurite began from opening in 1851 of its deposit in Baykal region then Russian stone processing factories have achieved a great skill in manufacturing of large art products (columns, vase etc.)
     In 1931 operation of the revealed deposit of lazurite on Pamir mountings was begun. To present time lazurite is known in two areas: in Southern Baycal (Malobystrinskoe deposit), and also on Southwest Pamir (lyadvargdinskoe deposit). The first deposit is extracted by opencast way, the second is extracted by underground way.
     Due to beautiful coloring and ability to get mirror polishing, lazurite is widely applied today as various inserts in rings, cuff links and other ornaments. Of it make a beads, vases, jewelry boxes and other wares. The crumb of lazurite is used at manufacturing mosaics, and also a high-quality ultramarine paint. The significant quality of lazurite were spent on facing of columns in interior of Isakievskiy cathedral in St. Petersburg; panels, fireplaces and other wares at furnish of lazurite room of the Peterhof palace in St. Petersburg.