Bright turquoise glass for cloisonne work was developed by the Chinese in the Yuan Dynasty, c14th century, and became the signature color for the Chinese name for cloisonne - Jing Tai Lan. Ming Emperor Jing Tai Blue. [Sallie pointed this out when I first became interested in cloisonne]

Beatrice Quette in her book Cloisonne has a chapter on the materials analysis of the glasses in Chinese enamel, and discusses how changing glass recipes might be useful in determining production dates.

The use of fluorite as an opacifier in Chinese turquoise glass struck me as noteworty, compared to antimony or bone ash in European glass.

Just in case anyone's interested....