Maru - Interesting choice. When ground, Ultramarine is more precious than gold when weighed gram by gram. Ultramarine was the finest and most expensive blue used by Renaissance painters. It was often used to make the robes of the Virgin Mary, symbolizing holiness and humility. It remained an extremely expensive pigment until a synthetic ultramarine was invented in 1826. That is fascinating stuff. It was like the AI of the 19th century art world!