A Jizhou 'Tortoiseshell'-glazed Bowl. Southern Song Dynasty (1127-1279). Photo: Christie's Images. The 'tortoiseshell' glaze was an innovation of the potters at the Jizhou kilns in Jiangxi province during the Song dynasty. Known as 'tortoiseshell' glaze, its name was derived supposedly from its similarity to the shell of a warm-water sea turtle known as the hawksbill.