Yixing clay (simplified Chinese: 宜兴泥; traditional Chinese: 宜興泥; pinyin: Yíxīng ní; Wade–Giles: I-Hsing ni) is a type of clay from the region near the city of Yixing in Jiangsu Province, China, used in Chinese pottery since the Song dynasty (960–1279) when Yixing clay was first mined around China’s Lake Tai. From the 17th century on, Yixing wares were commonly exported to Europe. The finished stoneware used for teaware and other small items is usually red or brown in color. Also known as zisha (宜興紫砂) ware, they are typically left unglazed and use clays that are very cohesive and can form coils, slabs, and most commonly slip casts. These clays can also be formed by throwing. The best-known wares made from Yixing clay are Yixing clay teapots, tea pets, and other teaware.
Zi Sha or Zi Ni (紫砂 or 紫泥; literally, “purple sand/clay”): this stoneware has a purple-red-brown color.
Zisha is a mixture of kaolin, quartz, and mica, with a high iron oxide content. It is mined principally at Huanglongshan and Zhaozhuangshan and has a somewhat sandy texture. The process of preparing the clay is lengthy and was traditionally regarded as a trade secret. Typical firing temperature is between 1100 – 1200 °C in an oxidizing atmosphere.