The use of ultramarine blue (lapis lazurite) in religious paintings of the middle ages became synonymous with depictions of the Virgin Mary. (theguardian.com)
Using a palette knife, make a 50:50 mix of ultramarine blue and white to establish a template for your mid-toned mixtures. (theguardian.com)
The big surprise came when I applied a blue - gray blend of French ultramarine blue and burnt sienna. (artistsnetwork.com)