For over 500 years, ultramarine was literally the most expensive material in the world — more precious than gold. Mined exclusively in Afghanistan, it had to travel overland across the entire known world before reaching European painters. The name means "beyond the sea" (Latin: ultramarinus) — it came from across the ocean. Patrons who commissioned paintings would specify in contracts whether ultramarine or cheaper substitutes could be used for the Virgin's robe.

Infinite, sacred, and deeply interior. Ultramarine is the blue of the mind looking inward — of deep meditation and vast space. It carries the full weight of its history: the sacred blue of the Virgin, the impossible blue of a clear sky, the deep blue of the unconscious. Psychologically it promotes introspection, calm, and a sense of infinite space.

The Virgin Mary's blue robe in Western art is almost always ultramarine — its expense signalled the importance of the subject. Painters kept their ultramarine locked away and used it sparingly. The discovery of synthetic ultramarine in 1826 democratised the colour — suddenly available to everyone, it lost its exclusivity while gaining universal use. Yves Klein's "International Klein Blue" (1960) is a specific formulation of synthetic ultramarine in a resin binder that Klein patented.