What exactly is petuntse? (mineral)
According to the Pottery Histories web site:


  Petuntse
  Petuntse is a historical Chinese term for rocks with a high content of
  mica and feldspathic minerals that have been used as one of the
  ingredients in the manufacture of Chinese porcelain. It is generally
  similar in composition and use to China stone. Petuntse, with china
  clay, forms the base ingredients for hard-paste porcelains similar to
  those produced in China in historic times. See China stone.  


and


  China stone (Cornish stone, Cornwall stone)
  China stone is a
  feldspar-rich mineral derived from partially decomposed granite. China
  stone includes feldspar, mica, fluorospar, quartz and other
  granite-derived minerals such as kaolinite, but lacks iron-bearing
  minerals.  China Stone is used worldwide as a flux in the manufacture
  of ceramic bodies and glazes. In the United Kingdom, the material is
  mined in one small area of Cornwall.


I don't know if this meets the degree of specificity that you were looking for.