Rock of the Month April 2022
Lapis Lazuli
Lapis is a unique metamorphic rock which holds historical and cultural significance across many continents and eras. Lapis lazuli is commonly composed of lazurite, sodalite, calcite, and pyrite. Many additional minerals are commonly found in lapis such as hauynite, nosean, diopside, lollingite, mica, and hornblende. The blue color of lapis comes from lazurite, a feldspathoid silicate mineral and sodalite, a tectosilicate.
Lapis lazuli is often formed through contact metamorphism of limestones, which often leads to lapis being found in and around marble. Lapis has a hardness of 5.5 on the mohs scale, a specific gravity of 2.7 - 2.9k g/m^3, forms in the cubic system, and has a vitreous luster. Lapis can be sensitive to heat as well as acidic and alkali liquids, however this doesn’t prevent the stone from being worked into jewelry. The quality of lapis is often determined by the richness and amount of blue present in the stone, meaning stones lower in calcite and pyrite are considered higher quality.
Lazurite is a complex sodium, calcium, feldspathoid mineral (Na,Ca) 8[(S,Cl,SO 4,OH) 2|(Al6Si6O24)] that forms an intricate lattice. The blue color of the mineral is caused by charge transfer between sulfur atoms within the lattice. This unique blue tone led the stone to being highly prized in jewelry, art, and its usage as a pigment.
Lapis artifacts have been dated as far back as 7570BC. Many different cultures over thousands of years have used lapis lazuli in their art, as signs of wealth, and as part of religious or cultural ceremonies. Oftentimes originating out of northeast Afghanistan, lapis was a key trade component and was exported throughout the Mediterranean and South Asia. There are many famous pieces of art using lapis, a few examples being King Tutankhamun's funeral mask, The Annunciation 1311, Guido Reni’s woman with a bowl, The Ishtar Gate, and the Hall of lapis at the Taj Mahal.
The stone is still mined in Northeastern Afghanistan as well as west of Lake Baikal, Russia, the Andes Mountains, Canada, Pakistan, Italy, and the United States, and at Dimitridon, you can take home a historical sample of lapis at our South Haven or Alexandria, Kentucky stores.
