Before we enter the topic of Zhu Ni Clay, we must discuss Duan Ni Clay.
So what is Duan Ni? In written Chinese, there are two letters for it. The first character is "緞", which means silk. It has a very similar pronunciation with "團" (Tuan) at Yi Xing, so this name probably came from literai at the time who thought "silk" would sound more elegant.
The second character is "團", which means "mass". This name basically describes the geological character of it, indicating it is a "mass of different ores." These different ores could be "Zi Ni" and "Green Mud," or "Zhu Ni" and "Green Mud" (which very rarely happen). You might notice already, "Green Mud" plays a very important role in Duan Ni. The composition of Duan Ni must have Green Mud in it, and must contain more than the other ores such as Zi Sha or Zhu Ni to classified as "Duan Ni". Duan Ni is a type of sedimentary rock that's a combination of Argillaceous Siltstone and Silty Mudstone. This gives Duan Ni an almost a clay-like texture on the surface when contact with skin, unlike Zi Sha's rocky/hard feeling, but still relatively more robust when compared to Zhu Ni.
below - The ore on the right is the original ore of Duan Ni, which is basicall white-grey in hue. The ore on the left is also Duan Ni ore after kiln firing at 1200 c. You might notice that the ore on the left shows some apparent signs of other ores as well.
below - Another closer look.....
below - Now we have introduced the "Duan Ni," it is time to reveal the identity of the green spot of the Di Zao Qin. Exactly, they are "Duan Ni." (緞泥)
below - And that's why it turns yellow after kiln firing.
Now let's discuss the final part of the mystical Yi Xing Ore - Zhu Ni. Some readers might already know what type of rock Zhu Ni is by now since we had discussed two types already - Argillaceous Siltstone and Silty Mudstone. These two types of sedimentary rock represent Zi Sha and Duan Ni respectively. Both have a very tough quality although Duan Ni tends to be softer and will mostly be found with Zi Sha in the same ore.
Zhu Ni, unsurprisingly, is is type of "Clayey Mudstone" and is not only a sedimentary rock, but some of them would also be a type of concretion rock. It is very unique to craft a teapot out of such an ore, and this is also one of the reasons why Zhu Ni teapots are so special.
Zhu Ni ore disintegrates easily in hand and when it makes contact with water, it is also very smooth and has a "baby powder" like texture. Despite its fragile structure, when fired it has the highest contraction rate of any Yi Xing clay (between 25% to 50%), and is also the most durable after firing.
Since the ore is extremely fragile, most of the older Zhu Ni teapots (Before 1950) were actually made from "Qing Shui Ni", (清水泥) a type of natural Zi Sha we mentioned in the previous article which was really common ore mined in Yi Xing. This type of "ancient Zhu Ni teapot" will have a Zi Sha as the structure, and applied Zhu Ni pulp as coloration for its exterior. By using this dual layered ore process, a teapot will not only have the Zhu Ni look, but will also has a high success rate after kiln firing.
Besides examining the geological aspect or ore to understand it, we can also find some references in the ancient texts by literati from Ming Era. The ancient text wrote as such: "石黃泥，出趙莊山，即未觸風日之石骨也，陶之乃變朱砂色. (Stone Yellow Mud was born from Zhao Zhuang Shan, and it was the "stone bone" which was untouched by wind and sun. Turn to Red or Pearl Sand after fire). Due to the ambiguity in ancient Chinese, the character "Zhu" (朱) has two meanings in the modern understanding - the first one is red obviously, since most of the Zhu Ni in the market has a red appearance. The second meaning is less heard of - "pearl". This means that such kind of ore has a pearl-like quality after fired. We will find out how pearl-like Zhu Ni is compared to Hong Ni (紅泥) in the later part of this article.
Most of the Zhu Ni came from two locations at Yi Xing. The first location is also where Zi Sha could be found the most - the Huang Long Shan (黃龍山). The second location is where most people know - the Zhao Zhuang Shan (趙庄山). Both locations have good quality Zhu Ni, however Zhu Ni from Zhao Zhuang is more desired today in the market because the place has been turned into a scenic tourist site, and also with proper extraction from the ore and firing temperature, Zhao Zhuang Zhu Ni will have more "colors to choose from" and better "water color" (水色) than Zhu Ni from Huang Long.
Let's stop the talking at this point and begin looking at the actual ore of Zhu Ni. By looking at it you would understand its fragility, the "colors" we mentioned, and how it is different from Hong Ni in the finished product.
below - The ore on the right is the original ore of Zhu Ni. This is the common type of Zhu Ni at Yi Xing, which local called "Little Hong Ni" (小紅泥), even though it is very different from Hong Ni (紅泥). After fired at temperature 1100 c. This type of Zhu Ni was not only found at Zhao Zhuang, but also at other locations in Yi Xing as well.
below - The concretion ore on the right is the "stone bone" that was mentioned in the ancient text, in which we can observe the yellowish color inside the hard and rocky exterior "as the bone" and numerous layers next to each other. Since it is like a rock at the exterior, the yellow interior was naturally "protected from wind and sun" as described in the ancient text. After firing, the yellow and other parts of the interior will turn more colorful like one on the left. Not every part of it is red, some other colors such as blue and yellow can also be noticed.
below - Here is how colorful the interior becomes after firing, (this was also our featured photo for our Yi Xing collection)
below- Such a kind of ore is also known as "Yellow Stone Yellow" (黃石黃). It is extremely rare and difficult to process into a teapot. It has an extremely low firing temperature at 1007 c, and has a 50% contraction rate. The darker layer of the ore can be processed into blue or yellow material for teapot making. This rare and special ore can only be obtained at an extremely high cost. So this type of Yi Xing ore was only used as "coloration" during the ancient times.
below - The picture here shows the interior part inside the yellow ore. The core is the oldest ore, and the further apart from the core the younger the mineral is.
At this point you might notice that all the Zhu Ni photo we have taken show some small fractures fallen off from the ore. These fractures reveal the ore's "fragility" which we have already discussed.
below - This Zhu Ni ore in the picture is known as "Di Zao Qin" type of Zhu Ni. It can only be found at the bottom part of the Zhao Zhuang Shan seam (more than 100 meters deep in the mine).
below - Here is the difference between Zhu Ni and Hong Ni. From color to texture they demonstrate totally different characteristics, although both look reddish after firing. Hong Ni (on the right) is a sedimentary rock, while the Zhu Ni ore on the left has a stone-like appearance.
below - Even the finished product shows a very different character. The Zhu Ni teapot (on the left) has a better "water color" (水色 / water color, a term used to describe the glossiness of the finished product). The glossiness shown here does not come from "tea seasoning" or any artificial material, but is the original texture from the ore itself. To achieve finished product with such a glossy "water color" appearance and texture not only requires patience and craftsmanship, but also good luck! (The teapot on the right is a Hong Ni product.)
In conclusion, Zhu Ni is a type of Clayey Mudstone which is a concretion ore. Not only does it have a soft and a "talcum powder" like texture, it also is relatively fragile and rare compare to other ores mined in Yi Xing. Despite the fragile character of the ore itself the clay itself when fired has a very high contraction rate and low firing temperature. The finished product is naturally glossy and silk to the touch.
We hope the following articles would help everyone who loves Yi Xing teapot to have a better understanding of this great gift from mother nature.
We hope you have enjoyed reading our Yi Xing article series!