Ultramarine

The pigment ultramarine is what lends the semi-precious stone lapis lazuli its characteristic deep-blue color. Chemically, it is an aluminum sodium silicate containing sulfide (e.g. (Na10Al6Si6O4S2)x ). Ultramarine has been used since ancient times. The earliest find was a Sumerian mosaic from around 3000 BC. Other examples come from the treasure chamber of the Egyptian pharaoh Rameses II (1290-1223 BC). The natural pigment is very expensive nowadays, as indeed it was in the past, and is therefore only rarely used. In 1828, the three chemists Giumet, Gmelin and K?ttig each independently discovered how to manufacture artificial ultramarine after attempts had been made to do so since 1795. This colorant, also known as sky blue, is widely used today for printing inks and other applications.

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