The Two Most Important Zisha Ore No-One Talks About

Introduction

Everyone knows about the famous types of Yixing Zisha, (If you don’t, check out my article about them [HERE]) but no one really talks about the less famous, but actually, much much more common Zisha ores, which are used for making the cheap mass-produced teapots and other everyday pottery products (bowl, vases, pitchers…).

To avoid getting confused it’s best to start with what Zisha actually is… So let’s jump right into it…

What is Yixing Zisha?

Yixing clay/ore is a clastic sedimentary rock, mainly siltstone and mudstone, which formed from lake deposits 350 – 400 million years ago, during the Devonian era. 

Usually, when people put Zisha ores into categories or types, they divide them by Zini, Lüni, Hongni, Zhuni, Tuanni. However, these are just a minority of the materials produced in the mines around Yixing. 

Usually, these mines are categorized as either Jiani (甲泥) or Nenni (嫩泥) mines, the same way as the most common ores in those mines. Because the more famous Zisha ores also come from these mines, therefore they share some common traits with the base ores of the mine.

Ores found in Jiani Mines
Ores found in Jiani Mines

For example, ores coming from Jiani mines (Jiani, Zini, Lüni, Hongni, Tuanni) are more like siltstones, made of larger particles, harder to weather, and break apart. While ores coming from Nenni mines (Nenni, Zhuni, Xiao Hongni) are more like mudstones, made of smaller particles and easily broken up by the weather or force. 

Ores found in Nenni Mines
Ores found in Nenni Mines

Zisha Jiani – 甲泥

Jiani is a siltstone and is the main raw material used for making everyday pottery products (vases, bowls, plates, etc.). Most Zisha belongs under the Jiani category, like Zini, Lüni, Hongni, Tuanni. As a result of the low supply of the aforementioned main Zisha ores, some of the higher quality Jiani ore is blended with other materials to be used as a substitute instead, in cheaper teapots. The main Jiani mines are Huanglongshan (黄龙山), Dongshan (东山), Xishan (西山), Nanshan (南山), Hufu (湖㳇) and other places. 

Raw Zisha Jiani Ore And It's Color After Firing
Raw Zisha Jiani Ore and It’s Color After Firing

The appearance of Jiani is similar to that of Zini, Lüni, Hongni and Tuanni. So it can be purple, brown, rusty red, grey colored. The prepared clay paste generally has good plasticity, slightly crispy while being formed, has a bit of a sandy feel to it, and a wide firing temperature range. Generally, it is fired at about 1100~1220℃, and the shrinkage rate is around 6%. The color after firing is similar to that of the popular Zisha categories, just a lighter, less punchy, more boring color, while also having more impurities. 

Zisha Nenni – 嫩泥

Nenni is a Clay mudstone, mainly produced in Hongwei Xiangshan (红卫香山) and the Zhaozhuang Shashan (赵庄沙山) area. It’s easily broken down by weathering, has a soft texture, slippery feel, while having good plasticity and bonding ability with other materials. It is most commonly used as auxiliary material to increase the plasticity of a clay mix in daily ceramics.

Raw Zisha Nenni Ore
Raw Zisha Nenni Ore

However, its firing temperature is relatively narrow, so it needs more precise firing. Generally, it is fired at about 1140~1160℃, and the shrinkage rate is about 7.5%. After firing it has a dark red, orangish color, with a more dry feeling surface, as opposed to Zhuni.

Color of Nenni After Firing
Color of Nenni After Firing

That is the reason some amount of Nenni is commonly mixed with other Zisha minerals so that it can improve the plasticity of the paste while increasing the strength of the teapot’s body and reducing the sintering/firing temperature. Which makes it easier to make bigger more complicated designs, while also making the firing of teapots easier, safer. It’s also common, to add some coloring oxides to Nenni, typically iron oxide, to create Zhuni like teapots that can be easily mass-produced, and sold cheaply. 


I hope this article was clear and informative for you. If you didn’t understand something or have further questions about the topic, please feel free to leave a comment.

In case I’d find new information or something contradictory, then I’ll update the article so that it can be used as a reference continuously.

Source:

  • Yixing Zisha Mineral by Zhu Zewei – 宜兴紫砂矿料 by 朱泽伟
  • 宜兴紫砂矿物原料研究 by 李珊
  • 宜兴陶土性能的研究 by 胡立勋
  • Compositional characterization of Zisha clay from the Yixing area (Jiangsu, China) by neutron activation analysishttps://doi.org/10.1016/j.microc.2019.04.031
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