Purple Sand
Yixing, Jiangsu Province, known in China as the "Pottery Metropolis", produces a much-valued red and boccaro ware - purple sand teapot. The first YiXing teapot was created during the Song Dynasty (960-1279).
Classic pot shapes ranged from the ordinary (vegetables, insects or simple objects in daily life) to the extraordinary (ritual vessels, convoluted rocks or mythical creatures).
To Chinese connoisseur, such teapots is regarded as the "ideal teapot". The material, called zisha (purple sand), is abundantly available in the locality. Although not as white or as fine as kaolin, it needs no glazing and, after firing, the product is solid and impermeable, yet porous enough to "breathe". A Yixing teapot enhances the tea brewed in it with respect to colour, smell, and taste. Its walls seem to absorb the tea and keeps its fragrance. In summer, it keeps tea overnight without spoiling. With hot tea inside, it does not scald the hand with purple sand being a slow heat-conductor. But in winter, it may serve as a handwarmer and may be left on a low fire to make certain types of tea which need simmering.
What's more, yixing teapot that is make from Zisha clay which is free of lead, arsenic, cadmium, and other toxic materials.The Yixing teapot has a fine and solid texture, a four percent water absorption rate, a very low thermal conductivity, and a double air hole design which enhances the pot's brewing properties. Statistics in China shows the mineral deposits are very healthy for people who has high blood pressure, high cholesterol. It promotes longevity.
Purple sand teapot should never be washed using detergents, but with water only and it's better to use each tea vessel for one kind of tea (white, green, oolong, or black) or sometimes even one variety of tea only.
http://www.chinainfoonline.com/ChineseArtsCrafts/Red_Ware.htm
