This one is certainly the most interesting piece of my collection of ancient yixing teapot. And for sure the most instructive in my personal research about understanding ZHUNI clay. Some years ago, I was looking after a thin wall yixing teapot of high quality to use it for brewing very fragrant, complexe and delicate tea, like FENG HUANG DAN CONG or GAO SHAN CHA from taiwan or high quality TIE KUAN YIN. The perfect teapot for such purpose must be accurate and give some mellowness...
When I went to my favorite teashop and most reliable source for ancient zhuni teapot ( Maison des Trois Thés in Paris), I saw some pot and my attention was attracted by one pot which appearence was completly different than others : the clay was like velvet or silk, very fine but without the typical buttery shiny wrinkeld texture of real zhuni. It was very mat, more like satin, no buttery look at all... This teapot was not fitting my idea of what genuine zhuni must be but the price of the pot was far more expensive than every other pot on the table... So I was at the same time curious and suspicious. And I asked the opnion of Master Tseng which was the best teapot among all the other teapot on the table, and she designed this one which according to her must be far better than the buttery looking pot... So I decided to trust her and bought it. Back at home, I did many testing and tasting. And after 4 years of use, I must say that this pot is really amazing. Even if it doesn't have the typical zhuni appearence, its performance are awesome. I used it mostly to brew Feng Huang Dan Cong and it deals really weel this challenge. The tea is fragrant, complexe, sweet, mellow, with a long and detailled aftertaste..
So after a lot of research and reading about what real zhuni is and how to identificate a genuine yixing, I must say that it is really quite difficult to tell just from the appearence of the pot.
The only truly reliable test to know if you have a real zhuni teapot in you hand is to try it and brew tea that you know perfectly.
If zhuni can be so different it is mostly beacause it come from sediments rocks, and also beacause it can be mixed or processed and fired according quite different ways.
But there is some indication that you can trust : the typical buttery wrinkeld surface texture, the particules of zhuni are much more smaller than other red clay (they are so small that you can't see them although there could be some larger particules in the main substance). The sound of zhuni is high pitched. There is always marks of shrinkage caused by the firing (this is one the main property of true zhuni ), sometimes shrinkage marks are obvious (and looks like wrinkles, or even like the skin of an old apple, they can even have cracks inside...), somtimes shrinkage is barely noticeable (and only can be seen with some particular angle of light reflexion on the surface...). But tasting is the only reliable way to know...
Some others pictures of this teapot :