## Clay Types and Their Characteristics Pear-skin clay fires to a pear-jelly color; light red clay fires to a pine-flower color; pale yellow clay fires to a bean-green color; dense clay fires to a light ochre color; pear-skin mixed with white sand fires to a pale ink color. The mountain's spiritual veins and networks, through ceramic firing and transformation, still reveal various luminous and extraordinary phenomena. Old clay, extracted from Tuanshan, is fired mixed with white sand in a starry pattern, pressed like pearls from heaven; when blended with sky-blue and stone-yellow, it produces various shades of antique coloring.[1] Modern geological surveys have further confirmed that the Yixing purple sand ore veins and their properties fundamentally accord with the records of Ming dynasty scholar Zhou Gaoqi. **Purple Clay** | **Benshan Green Clay** | **Red Clay** "Purple clay" (*zini*) appears purple-red in its raw ore state, with fine silver specks glittering throughout. After firing, it becomes dark red. Its main component is hydromuscovite, containing varying amounts of kaolin, quartz, mica, and iron compounds. The clay body has high strength and low drying shrinkage rate, providing excellent technical conditions for diverse and complex forming. "Old clay" (*laoni*), also known as "Benshan green clay," is found in the layer between the purple clay stratum and the rock plate. The raw ore appears egg-white in color, with a surface smooth as fat—hence also called "interlayer fat" (*jiazhi*). After firing, it becomes pear-skin jelly color. Due to the low yield of Benshan green clay and its difficulty in forming pottery, it is typically used as a slip coating on the surface of purple sand wares, or mixed with appropriate amounts of purple clay to create "duan clay (tuan clay)" for use. "Stone-yellow clay,"[2] also known as "red clay," appears orange-yellow in its raw ore state. The ore layer is located at the bottom stratum of tender clay (*nennni*). According to *The Yangxian Famous Teapot System* (*Yangxian Minghu Xi*), "Tender clay, extracted from Zhaozhuang Mountain, can be blended with all colors. Its upper layer is sticky and fatty, suitable for building, as it becomes elastic after firing."[3] Red clay is the clay material located at the bottom of the tender clay ore layer. The ore formation is fragmentary and requires manual selection. Due to its varying iron content, after firing it transforms into vermillion, vermillion-purple, or crabapple-red colors. Because of its scarcity, it is generally only used as a decorative slip for purple sand clay bodies, or for making small vessels. Today, Zhaozhuang red clay... --- [1] Zhou Gaoqi (Ming dynasty), *The Yangxian Famous Teapot System* (*Yangxian Minghu Xi*), in Han Qilou, ed., *Modern Translation of Ancient Purple Sand Texts* (Beijing: Beijing Publishing House, January 2011), p. 7. [2] Ibid. [3] Ibid.