Structure : various
Hardness : 5.5
Specific Gravity : 2.8
Refractive index : 1.5
Doubly Refracting (bi-refraction) : none
The beautiful blues in paintings from the Renaissance are thanks to the blue of lapis lazuli, the opaque blue gem material that was the secret ingredient in ultramarine, the valuable pigment that all the old masters used to capture the rich blues of the sea and sky and the robes of the Virgin Mary. The color wasn't duplicated by any other substance until 1834 but even now, some argue there is no substitute: unlike other pigments ultramarine centuries old still glows with rich color today.
Lapis lazuli is a dark blue microcrystalline rock composed primarily of the mineral lazurite. It often sparkles with golden pyrite inclusions, like stars twinkling against the blue firmament.
Connoisseurship of Lapis Lazuli was already ancient in the Renaissance. The city of Ur had a thriving trade in this blue gem as early as the fourth millennium B.C. Lapis Lazuli was among the treasures of Mesopotamia, Byzantium, Egypt, Persia, Greece and Rome.
Lapis Lazuli was also thought to be strong medicine. The Romans believed it to be a powerful aphrodisiac. In the Middle Ages, it was thought to keep the limbs healthy and free the soul from error, envy and fear.
In Russia, the imperial family used lapis lazuli on a grand scale, including the columns of St Issac's Cathedral and wall paneling for the Pushkin Palace in St. Petersburg.
As befits a gem that has been international currency for millennia, the name lapis lazuli is mélange of languages. From the Latin, lapis means stone. From the Arabic, azul means blue.
Lapis lazuli is still mined at the deposits of the ancient world in Afghanistan. Today lapis lazuli is also mined in Chile. Small quantities are also produced in Siberia, in Colorado in the United States, and in Myanmar.
Lapis lazuli is somewhat porous and should be protected from chemicals and solvents. Lapis is not very hard at 5.5 and should be protected from other jewelry when stored to avoid scratches. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect.