The original Ultramarine blue was made from the semi-precious stone lapis lazuli. Processes for making the pigment in the West date from the 12th century, but it was being made six centuries earlier in Eastern countries. The name comes from the Italian azzurro oltremarino, which means "blue from beyond the sea." Much of this stone originated in the mines of Sar-e-Sang, Afghanistan, very near the place where the Taliban blew up those venerable Buddhist statues a few years ago.
Ultramarine blue was manufactured by a complex process that separated the lapis from the gray gangue rock with which it is associated in nature. Genuine Ultramarine was the costliest of pigments, worth more than twice its weight in gold. Mediaeval princes doled it out, and artists carefully washed their brushes to save the last precious bits. Unfinished works such as Michelangelo's Entombment, and others, were probably brought to a halt because artists couldn't get enough of the stuff.
These days, Ultramarine blue is known as a "furnace product," made with a roasting process of an equally magical nature. Ultramarine blue is reported to be one of the most useful of colors, permanent in all applications except fresco. In full strength or cut with white, yellow ochre or gamboges, the tone is most ethereal. When used as a neutralizer with all the warmer tones, it makes for sophisticated grays. In watercolour, Ultramarine blue works magic because of its larger molecules and the consequent "graining" effects.
Ultramarine blue seems to breathe. It represents the air between the viewer and the viewed. Aerial perspective can't live without it. More than any other colour, Ultra blue holds sky-magic, the zenith, the spiritual--closest thing to heaven--and the most profound of the colour mysteries. A tube of Ultra is at once jewellry and atmosphere. Blue will always be loved. "Just as there are connoisseurs of wine, there are connoisseurs of blue," said the French writer Colette.
PS: "Blue is everlastingly appointed by the Deity to be a source of delight." (John Ruskin)