Quoted chrl42 from another thread.
Original Da Hong Pao ni was from Huang Long mountain. And it was thought the most 'reddish' clay to be found, contained highest iron and enormous shrinkage rate. Virtually all 'real' Da Hong Pao ni has gone from the sight and I read in the news it was once sold more expensive than gold.
But backed by demand, yixing crafters imitated the effect of Da Hong Pao ni, usually by containing red iron powder or Shi Huang(one source of Zhuni).
I once have seen Da Hong Pao pots in Maliandao, very sleeky texture and weighed a lot. My expression was like I was touching a metal of some sort. All of em were over 500 USD.
