The Awasedo Bearing Mountains of Kyoto
There is a diagram of the structure of the japanese awasedo posted here and there, copied and refered to that looks something like this. Click on the drawing to make it larger.
Now I have to admit that my inserted drawing here and the ones below look like those of a child, but I assure you that the mine structure of all of the mines in the Yamashiro of Japan has little if anything to do in the way as depicted with those stone strata all neatly are stacked up on top of each other showing Aka-pin, regarded as the softest stones down to Shiro Suita as the hardest as a factual way to explain why some stones are harder than others, or why some stones cost more, or why stone mined 60 or 100 years ago are not all that different from each other. There are vast differences between stones at all price points and from all mines, and as I will explain below, some of those differences are very logical.
The best of the best mines are already closed and the best of the best stones have already been sold. This is an harsh statement at face value so allow me elaborate.
The first mines in the Yamashiro area of Kyoto were founded and developed about 800 years ago. While the record of the first discovery in 1190 lacks some detail and largely concerns the presentation of the stone to the regent in Kyoto for his inspection and approval, we do know that it resulted in the creation of the title “keeper of the mine” for the finder Honma Tou-zaemon Toki-nari. Later in 1230 the title also granted the holder some exclusive rights to mine the stone on the site of the original discovery.
The name Yamashiro means Mountain Castle or Mountain Fortress, and this area of rural Kyoto was retained in those days as a fortified retreat and place of worship for the various Buddhist and Shinto sects who in those days of civil war and strife were occasionally called upon to defend themselves with arms. These mountainous lands were and still largely are owned and maintained by those very same sects and the locations of the historic mines that we hear so much about; Nakayama, Shinden, Okudo, Ohira, Narutaki, Ozaki and the 20 or so others were established on those private properties. From the very beginning the mine operators have been basically only leasing the mineral rights from the religious sects on a year to year basis. As a matter of first hand knowledge I know that the lease of one current mine is based on a bow or handshake with the dollar value mineral rights lease equaling more or less that of an expensive bicycle.
The first sharpening stone found in the Yamashiro was most likely just picked up by Honma Tou-zaemon Toki-nari as a loose rock, and probably that this happened on the crest or a ridge of Mt. Shobudani. At the higher elevations of these low windblown mountains the rock lays bare, is easily seen and exposed to the elements while at the valley floor and up mountain sides and into and through the tree line there is as much as 40 meters of topsoil and plant life to dig through before you can find the vein of awasedo. This is why I think it is logical that the first walker who happened upon the sharpening stone material just picked up a loose stone. His next step would have been to locate the source vein of the stone.
It is recorded that the earliest mines were dug at the higher elevations were the mineral vein broke through the surface and was exposed. Over the next eight centuries the mine tunnels were dug at successively lower elevations as the stone stock was depleted or panned out in the tunnel above. The trick was for the miners to track and relocate the vein as it threaded its way down through and along the interior of the side of the mountain, lots of test tunnels were necessary over the years. The mine tunnels established were and still are set with narrow entrance, the tunnel dug horizontal and slightly inclined to facilitate removal of stone. Where the tunnels intersected the awasedo stone sheet they were hollowed out to look like large rooms as they were worked from side to side across the face, not deeper into the interior of mountain.
The stone deposit for awase toishi mined in Yamashiro appears within the mine geology as layers, these layers or strata are called in Japanese as Sou, and the sou are stacked like the pages of a book being back to front to back and so on. The book in this case is not laying down flat on a table but instead is standing up so the sou run vertical along and up and over the face of the mountain. Because of this, as you enter the mine tunnel you will be walking through and past each layer as they are stacked as vertically as the mountain is steep. If you go beyond the awasedo mine geology, the sou, you will hit the solid bedrock or the core of the mountain. So think of it as the stone layer with the awasedo being like a shield or skin over the mountain core.
This shield, if all were bare of vegatation on and around it would now look like a scab or patch as it lay on the mountain. Although as it was formed millions of years ago as a flat sheet of sediment, when it was scraped off the Pacific Plate as it reached Japan this flat sheet became in some areas distorted and torn into patches as in the Tamba Terrane and in other nearby places rolled or folded as in the Ultra Tamba Terrane. Also because the mountains beneath the sheet were still rising and forming, this vulnerable sheet was torn and seperated into isolated pieces or patches even further so that the indigeneous rock shows promininently between the patches. The drawing below illustrates such a patch as it lays below the suface of the surrounding mountainside and topsoil material.
Between the various layers of useable stone are original occurrence deposits of waste material that is not suitable for sharpening stone called Gokume, where the gokume meets the awasedo some of it is retained and then it is called Kawa. These good layers of stone are anywhere between 6 inches to 2 feet thick with the grain of the stone running parallel to the layer. The waste gokume is usually several inches in thickness and of variegated darker colors of rough hard material. There are about 80 distinct strata that make up the mines geology in the Yamashiro area and the total thickness including the waste runs to or slightly more then 45 feet thick.
The mineral deposit that represents the body of rock dug for sharpening stones is interchangeably called awase toishi, awase-to or awase-do, and it lays like a shallow patch or scab that runs up and over and around the low mountains of Yamashiro in a generally westerly direction out and beyond the city limits of Kyoto. This patch is known as the Tamba Terrane and the Ultra Tamba Terrane. This same layer or terrane of rock in several different configurations extends somewhat further in all directions, but the stone found in the outlaying areas is not of the same superior quality as that found in the Yamashiro area located in and around the small town of Umegahata. The accepted center marker for the whole mining region is the peak of Mt. Atago and from there the divisions between the eastern or Higashi-mono, and the western Nishi-mono mines are defined.
Because the Tamba Terrane and the Ultra Tamba Terrane were scraped off as a accretion wedge during the subjection of the Pacific Plate as it dove under the Asian Plate, these mountain surfaces were formed from more ancient seabed material dating to the Triassic and early Jurassic periods a couple hundred millions years ago. The terrane as it lays forms a covering over both the valleys and peaks of the area. Clicking on the Drawings below will enlarge them.
This drawing below shows a conception of the compaction ratio of the same thickness of several layers or sou of mineral as it is compacted by the gravity of the enormous of the weight of the mountain side above.
As you can see the weight of the mountain and its vertical slope should have a direct relationship to the compaction ratio of the metamorphic sedimentary stone that the Tamba and Ultra Tamba Terrane is composted of. In the very steep regions and at the lower elevations the clay binders of the awasedo stones are forced to compress. This compression along with any heat created by friction are other factors in the metamorphism of the silica, radialaria and clay components of the stone that makes up the awasedo stones of the Tamba Terrane in and around Kyoto.
Another important factor in the Tamba Terrane is the introduction of free flowing ground water at the lower elevations that can carry disolve minerals. Because of Japan’s unusual amount of moisture from rain the watertable levels can be quite elevated about the valley floors. This intrusion of water can disolve some of the original minerals such as found in clay and introduce alternate minerals, or may just remove those water soluable minerals all together leaving voids that are subject to compaction.
I speculate that:
In the Hon Guchi (or Cuchi) Naori in the Umegahata area the stone layers or sou are positioned more or less as they were created in layers where the Akapin is closest to the surface, the Tenjyou is next leading to various Tomae and Suita and finishing with the farthers from the surface the Shiro Suita layer. In the Chu Ishi Naori found on the outskirts of Umegahata all of those various sou layers are found in an integrated sequence with out gokume inbetween the sou, like they were rolled or tumbled together. Finally in the Ai Ishi Naori the Shiro Suita layer is found in the shallowest layers while the Akapin and Tenjyou are found in the middle. This Ai Ishi Naori is if I am not mistaken the Ultra Tamba Terrane (introduction Ultra Tamba Terrane
I am not a geologist, that must be apparent, but these simple changes that have occured in the nature of the awasado stones structure are well known. These are some of the main reasons why that the stone harvested from the mines like Nakayama and others was in the early days from about 1390 to 1860 of a softer consistancy in general: because it was dug at the higher elevations, and why the stone harvested durning the modern era from around 1860 to present is of a harder nature (unless it was freshly harvested at a higher elevation in a new mine discovery, however none are known to exist) because it was all dug at the lower elevations including below the watertable at the valley floor.
The modern era great wars that Japan fought including; the Sino-Japanese of 1894, invasion of Taiwan, Russo-Japanes war, WW1, then the 2nd Sino war of 1937, WW2 were devistating to the mining community of Yamashiro because if it were not for these wars and the demand for abrasives, most of which were used to hone the swords which most soldiers still carried in some form and the housing and rebuilding booms after WW1 & WW2, we might still have freshly harvested awasedo from the upper reaches. But this is not so. Almost all of the mines in the Umegahata area were closed before 1930 and the rest soon after due to depletion, the stone was all dug and trucked off. One of the last mines, Narutaki was finished off with steam shovels at the valley floor and bull dozed closed for good. The Nakayama mine itself was, in a ditch last effort, below the watertable in 1965, and the nearly verticle mine shaft had to be pumped as they worked. There is even a photo of Kato-san in the mine wearing a raincoat and rubber boots. The stone from that tunnel, or more correctly, shaft, were ink stamped by Hatanaka Toishi Company with rope and tackle logo to signify that the stone was lifted up from below, much of this stone was useless.
Japan, the land of the largest and oldest wooden buildings in the world, of woodworking guilds that extended unbroken for 500 years, of blacksmiths that created some of the finest swords in history which were all sharpened on natural japanese stones, of modern woodworkers who compete to shave with their handplanes continuous wood shavings in the 4micron range. These men and women had access to those stones. Why now are the mostly tourist oriented stores in Kyoto and Tokyo filled these days with hard, harder and hardest mostly gray stones? Because they are leftovers. Why are colored stones like yellow kitta, iro tomae for purples, reds and greens and white suita so rare and expensive? Because the crafts people in Japan hold them dearly.
Now I hope the users of natural japanese awasedo will have a broader perspective on why, when, where and how the current state of mining and selling these treasured beauties stands right now. There are still some old timer stones out there, and just like the vintage mined Coticules of the 1880-1910s the character of these stones is well worth digging for.
best wishes, Alx