ROYAL BLUE ENAMEL 18k (750 thousandths) yellow and white gold brooch featuring a flowering branch in richly textured gold, with details and foliage paved with small 8x8-cut diamonds of beautiful colour and purity. The five flowers have petals enamelled in transparent royal blue enamel on engraved gold, illuminated by diamond centres. Unsigned jewel. The enamel is slightly missing on two of the petals. Size: 7.9 x 3.3 cm. Gross weight: 23.1 g. Transparent royal blue enamel was used in some of the finest creations of the 19th and early 20th centuries, notably by the Russian jeweller Peter Carl Fabergé who, in 1896, produced a blue egg with twelve monograms for Tsar Nicholas II of Russia. The use of this transparent royal blue stems from the discovery of cobalt-based blue by French chemist Louis Jacques Thénard, who marketed the colour from 1802. Renowned for its stability, cobalt blue is highly resistant to temperature variations, making it ideal for meticulous jewellery. The brooch presented here is a tribute to this meticulous knowledge of enamel application and firing. In the round on engraved gold, the enamel illuminates the composition with great precision in its application.