Ultramarine Blue

\-mә-ˈrēn\ n [ML ultramarinus coming fr. beyond the sea, fr. L ultra- + mare sea] (1598) Na₆Al₆Si₆O₂₄S₂ (light); Na₇Al₆Si₆O₂₄S₃ (Medium); Na₈Al₆Si₆O₂₄S₄ (Dark). (1) A natural type of mineral origin. It is also known as genuine ultramarine and lapis lazuli. (2) The synthetic types are produced in several shades by heating sulfur, clay, soda ash and a reducing agent. They have good lightfastness and