The earliest known example of cobalt aluminate glass dates to a lump from about 2000 BC in ancient Mesopotamia, very possibly intended for use as a pigment; it was rare until the modern era. Cobalt oxide smalt appears as a pigment in Egyptian pottery about five centuries later, and soon after in the Aegean region, and this is the pigment normally known as "smalt". In paintings, smalt has a tendency to lose its color over a long period, and is little used today. However, when used in ceramics for underglaze decoration, it keeps its colour well, and is the main blue used in blue and white pottery from a wide range of dates and areas, including Chinese blue and white porcelain from the Yuan and Ming dynasties, Renaissance Italian maiolica and Delftware.