Expensive but sublime. Ephemeral, shifting blues.
Cerulean Blue is made from cobalt tin oxide and cobalt chromium oxide, it was discovered by Andreas Höpfner in 1805, but not used in an artists' paint until 1860, when it was sold as coeruleum by George Rowney. Essentially it could be considered cobalt blue with a stronger green hue, a nice image of Cerulean Blue pigment is below.
It is a velvety and muted blue, distinct from the more primary blues like cobalt and phthalo, it has a wonderful lightness once tinted with white. Like all cobalt based paints it is easy to handle and subtle. The safflower oil maintains these subtle, delicate blues over time, avoid any yellowing which in this situation would actually increase the green!
Pigment - Oxides of Cobalt and Chromium, PB36
Vehicle - Safflower Oil, Consistency - Soft Butter