The flakes of biotite in the present lot are a form of mica, which is sprinkled as tiny flakes onto the inner layer of glass. This technique was probably introduced to the Imperial workshops by the Bavarian Jesuit missionary Kilian Stumpf, who was director of the Imperial Glassworks from its inception in 1696 until he died in 1720. This type of mica is found in the Bavarian forests and was used in Bavarian glass-making. For a discussion of the technique, and another example of this rare type in blue glass, see Moss, Graham, Tsang, A Treasury of Chinese Snuff Bottles, The Mary and George Bloch Collection, Vol. 5, Part 1, Glass, Hong Kong, 2002, p. 167, no. 722. Another example including fragments of blue glass as well as biotite from the Meriem Collection, was offered in these rooms, 19 September 2007, lot 652.