1. where is Nakayama? What kind of terrain?
Nakayama whetstone—it is a legendary existence that is not unknown in the world of natural whetstones. Among them, “Nakayama’s Tozen, Asagi, and Zuita” and “Kurumaguchi” are regarded as the pinnacle of final sharpening, and are outstanding in both rarity and performance. So, what kind of place is Nakayama?
Nakayama” is the common name for an area located northwest of the Sanbi area in the back of Ukyo-ku, Kyoto City. The name “Nakayama-cho” and “Nakayama Ishiyama” can be seen on the map, and the area is located a little further into the mountains from Sagano. The elevation is about 200 to 300 meters, and the terrain is more like a “hill” or “hillside” than a “mountain” in general.
When you actually visit, you will find a series of mountain paths that require no hiking shoes, and a natural forest that now stands quietly behind a residential area. From its “unassuming” appearance, it is hard to imagine that a natural whetstone, one of Japan’s representative whetstones, can be found here.
2. the geology of Nakayama and the secret of the grinding stone layer
So why has this “inconspicuous hill” called Nakayama produced some of the world’s finest grinding stones?
The reason lies in the special geological formation that lies beneath the ground.
The Nakayama formation is a slate layer called “Honkuchi-nari,” which is composed of deep-sea mud that has been compressed and metamorphosed over a long period of time. It contains abundant fossils of tiny siliceous plankton called Radiolaria, which function as natural ultra-fine abrasives.
Nakayama’s slate has undergone low to moderate metamorphism, and is neither too hard like chert nor too soft like mudstone, making it ideal as a grinding stone. Furthermore, the natural weathering of the rock tends to bring up fine particles on the surface, which provides an excellent sliding feel and finish.
What is noteworthy is the richness of individuality of each layer. Nakayama has many overlapping layers with different abrasiveness, hardness, and appearance, such as “Zuita,” “Tozen,” “Hachimai,” “Tatei Zuita,” and “Kurumaguchi Zuita,” and they look as if they are different stones depending on where and at what depth they were mined.
3. history of mining and local conditions
The history of grinding stone mining in Nakayama began at the end of the Edo period and reached its peak between the Meiji and early Showa periods. Especially after the Meiji period (1887-1912), knife smiths and cutlery merchants from Osaka and Tokyo competed with each other to purchase the stones, and the grinding sounds of quarrying were always heard in the mountains.
There are three main mining methods: **open-pit mining, horizontal tunnels, and vertical tunnels**.
- Open-pit mining (cutting slopes in a stair-step pattern) for relatively shallow cesspool layers, etc.
- When targeting a doorway, etc., dig a **horizontal tunnel (horizontal tunnel)** and follow the strata.
- It is said that the Kurumuchi Formation was targeted using vertical wells that dug down 10 to 15 meters vertically.
All such excavation was done carefully by human eyes and hands, relying on “nodules” (natural cracks). This is truly a world of craftsmanship, where good layers are determined by the “sound,” “color,” and “sparkle” of the stone.
Today, mining of the Zhongshan whetstone has practically come to an end, and only old tunnels, crumbling stone steps, and a few traces of the exposed whetstone layer remain in the mountains. Nevertheless, “Zhongshan Stone Mountain” as a place name still remains on maps and is secretly popular as a pilgrimage site for whetstone fans.
4. How a humble topography gave birth to world-class grinding stones
After hearing all this, you may be thinking, “Huh? Then why wasn’t the mountain higher?” You may be wondering, “Then why wasn’t it a higher mountain?
In fact, the fact that Nakayama was not “too mountainous” may have been a positive factor for the grinding wheel.
- Elevation is not too high, so the strata are easily preserved without collapsing
- Geothermal heat and metamorphism were not too strong, and the “intermediate hardness” suitable for grinding stones was maintained.
- It was easy to excavate by hand and convenient to carry out.
In other words, although Nakayama is a humble “backwoods” area, the geology and environment were ideal for grinding stones.
summary
Zhongshan is nothing more than a small hill in terms of topography.
However, what lay beneath was a treasure trove of the world’s highest grinding stone layer.
Geologically, the best natural abrasive stone material, composed of honkuchi-bearing slate, rich in radiolarians, and undergoing just the right metamorphism to be both smooth and abrasive, was lying dormant.
The Nakayama Grinding Wheel, which is now called “fantastic,” was created by the eyes and hands of craftsmen from the Edo period to the Showa period.
Great value born from a small mountain – that is the truth of the place called Nakayama. Power (Kinin-kun style)